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november 2023
17nov11:00 am12:00 pmGabriel AeppliETHZ, EPFL, PSI (Switzerland)11:00 am - 12:00 pm KST
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Gabriel Aeppli Affiliation: ETHZ, EPFL, PSI (Switzerland) Research Interests: Physics, Nanotechnology, Synchrotron Title: Viable qubits
Event Details
Gabriel Aeppli
Affiliation: ETHZ, EPFL, PSI (Switzerland)
Research Interests: Physics, Nanotechnology, Synchrotron
Title: Viable qubits in noisy environments
Abstract: Quantum sensors and qubits are usually two-level systems, quantum analogs of classical bits assuming binary values ‘0′ or ‘1′. They are useful to the extent to which superpositions of ‘0’ and ‘1’ persist despite a noisy environment. The standard prescription to avoid decoherence of solid-state qubits is their isolation via extreme dilution in ultrapure materials. We demonstrate a different strategy using a rare-earth insulator which realizes a dense random network of interacting two-level systems. Qubits with ultralong decoherence times emerge within this network because of rather than in spite of the interactions.
Time
(Friday) 11:00 am - 12:00 pm
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Karl-Heinz Ernst Affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology Research Interests: Surface Science, Chirality, Molecules
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Karl-Heinz Ernst
Affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology
Research Interests: Surface Science, Chirality, Molecules at Surfaces
Title: Magneto-chiral selectivity, spin-filtering, Kondo physics and topological self-assembly of helicenes on metal surfaces
Abstract: Soon after his seminal discovery of molecular chirality Pasteur suggested physical fields as its origin and assumed that magnetic fields must be the source of chirality in the universe. Lord Kelvin refuted Pasteur’s suggestions and made clear that magnetism has no chirality. In 1894, Pierre Curie proposed that parallel and antiparallel alignments of electric and magnetic fields will induce chirality, but such chiral influence must vanish under conditions of thermodynamic equilibrium. We report that single helical aromatic hydrocarbons, so-called helicenes, undergo enantioselective adsorption on ferromagnetic cobalt surfaces. Spin- and chirality sensitive scanning tunneling microscopy (STM) reveals that molecules of opposite handedness prefer adsorption onto cobalt islands with opposite out-of-plane magnetization. As mobility ceases in the final chemisorbed state, it is concluded that enantioselection must occur in a physisorbed transient precursor state. Such observation suggests electron spin-depend van-der-Waals forces. Simultaneous measurements of the tunneling current through both enantiomers on a given Co nanoisland yields a magneto-chiral specific conductance of up to 50% for single helicene molecules, thus refuting previously proposed ensemble effects as origin of chiralityinduced spin selectivity. Our results open the opportunity towards new single-molecule spinvalve devices and shine light into the origin of the so-called chirality-induced spin selectivity (CISS).
Time
(Tuesday) 1:00 pm - 2:00 pm
02nov2:00 pm3:00 pmYou-Shin NoKonkuk University, Seoul2:00 pm - 3:00 pm KST
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You-Shin No Affiliation: Konkuk University, Seoul Research Interests: Low-dimensional optical nanomaterials and nanostructures and nanodevices
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You-Shin No
Affiliation: Konkuk University, Seoul
Research Interests: Low-dimensional optical nanomaterials and nanostructures and nanodevices
Title: On-Demand Hybrid-Integrated Photon Sources
Abstract: Silicon (Si) photonics has been receiving substantial attention as an integration platform in photonics research, owing to the ability to manufacture low-cost, compact integrated circuits. However, realizing efficient and high-quality light sources remain a major challenge. In this talk, I briefly discuss the recent progress of the photonic integration technologies and report on new developments of on-demand, align-transferrable micro-transfer-printing including several micro-manipulation techniques which are useful for addressing key challenges in photonic integration. First, we report on-chip transferrable low-threshold microdisk lasers by utilizing the microstructured polymer-assisted transfer-printing technique. In this work, we designed and fabricated an adhesive PDMS microtip and utilized it to micro-transfer-print single microdisk onto a small Si-post structure [1] and successfully operate rich lasing actions and couple the laser emission to a Si waveguide. Second, we also report on an all-graphene-contact approach to introduce the transparent and flexible electrical contacts to a vertically p-i-n doped active semiconductor nanostructure and to operate it by pulsed current injection [2,3]. Finally, we report on a recent result of an on-demand minimal gain-printed continuous-wave nanolaser-on-silicon at room temperature. The method and techniques in this talk can be very useful to facilitate light source integration in Si photonics and further help to realize high-density ultracompact photonic integrated circuits.
Time
(Thursday) 2:00 pm - 3:00 pm
october 2023
26oct1:30 pm2:30 pmUwe R. FischerSeoul National University1:30 pm - 2:30 pm KST
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Uwe R. Fischer Affiliation: Seoul National University Research Interests: ultracold quantum gasesmany-body physics, analogue gravity, quantum metrology, quantum
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Uwe R. Fischer
Affiliation: Seoul National University
Research Interests: ultracold quantum gasesmany-body physics, analogue gravity, quantum metrology, quantum simulation
Title: Quantum Simulation, Quantum Metrology and Quantum Engineering at SNU
Abstract: After a general introduction into the research activities of my Theory of Cold Atoms group at Seoul National University comprising, inter alia, fields as mentioned in the title, I will focus more specifically on the ramifications of the genuine quantum resources entanglement and steering onto two rather diverse phenomena: The analogue of cosmological particle creation in the early Universe (quantum simulation) and the usage of entanglement to enhance the charging power of quantum batteries (quantum engineering).
Time
(Thursday) 1:30 pm - 2:30 pm
24oct11:00 am12:00 pmLucas SchneiderUniversity of California, Berkeley11:00 am - 12:00 pm KST
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Lucas Schneider Affiliation: University of California, Berkeley Research Interests: Scanning Tunneling Microscopy, Superconductivity, Topology in Condensed Matter Physics,
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Lucas Schneider
Affiliation: University of California, Berkeley
Research Interests: Scanning Tunneling Microscopy, Superconductivity, Topology in Condensed Matter Physics, 2D Materials
Title: Superconductivity in atom-by-atom crafted quantum corrals
Abstract: Gapless materials in electronic contact with superconductors acquire proximity-induced superconductivity in a region near the interface. Here, we investigate the most miniature example of this so-called proximity effect on only a single quantum level of a surface state confined in a quantum corral on a superconducting substrate, built atom-by-atom using a scanning tunneling microscope. Whenever an eigenmode of the corral is pitched close to the Fermi energy by adjusting the corral’s size, a pair of very sharp particle-hole symmetric states is found to enter the superconductor’s gap. By comparison to a resonant level model of a spin-degenerate localized state coupled to a superconducting bath, we identify the in-gap states as scattering resonances theoretically predicted in 1972 which had so far eluded detection [1]. We further show that the observed anticrossings of the in-gap states indicate proximity-induced pairing in the quantum corral’s eigenmodes [2]. Based on these insights, I will discuss the implications on induced superconductivity in the surface state of noble metal Ag(111) grown on superconducting Nb(110). Notably, we find that the lifetime of electronic states is strongly enhanced by the presence of a proximity-induced bulk gap. Finally, we study how magnetic adatoms interact with the corral’s eigenmodes. Understanding their coupling eventually allows us to tailor a mirage effect [3] of Yu-Shiba-Rusinov sub-gap states induced by Fe atoms [4].
Time
(Tuesday) 11:00 am - 12:00 pm
06oct3:00 pm4:00 pmChi ChenAcademia Sinica, Taiwan3:00 pm - 4:00 pm KST
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Chi Chen Affiliation: Academia Sinica, Taiwan Research Interests: SNOM, TERS, AFM, Spectroscopy of Single molecules and nanomaterials Title
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Chi Chen
Affiliation: Academia Sinica, Taiwan
Research Interests: SNOM, TERS, AFM, Spectroscopy of Single molecules and nanomaterials
Title:
Combing Photon with SPM for STM-EL, TERS, and SNOM
Abstract: Combing optics with scanning probe microscopy (SPM) enables new possibilities of cutting – edge discoveries , such as tunneling induced electroluminescence (STM – EL), tip – enhanced Raman or photoluminescence spectroscopy (TERS/TEPL), and aperture or scattering scanning near – field optical microscopy (a – /s – SNOM). In this talk, I first introduce the basic principle of confocal optics and the light path design for tip illumination/photon collection. The instrumentation of both STM – optics and A FM – optics will be presented and compared. Three different categories of experiments are included: (1) STM – EL from single molecules and atomic chains at cryogenic temperatures and UHV environments. (2) STM – TERS of carbon nanotubes under ambient conditions. (3) AFM – SNOM of 2D materials in ambient conditions and AFM – SNOM of lipid bilayers in liquid.
Time
(Friday) 3:00 pm - 4:00 pm
september 2023
Event Details
Rudolf Haindl Affiliation: Max Planck Institute for Multidisciplinary Sciences and Georg August University of Göttingen (Germany) Research Interests:
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Rudolf Haindl
Affiliation: Max Planck Institute for Multidisciplinary Sciences and Georg August University of Göttingen (Germany)
Research Interests: Physics, Electron Microscopy
Title: Coulomb-correlated few-electron states in a transmission electron microscope beam
Abstract: Correlations between electrons are at the core of numerous phenomena in atomic, molecular, and solid-state systems. However, harnessing free-particle correlations remains challenging, with the recent implementation of nanoscale single-electron sources [1] and observation of anti-bunching in electron beams [2, 3, 4]. A powerful approach to induce strong inter-electron interactions is femtosecond-triggered photoemission from nanotips [5,6] with high spatial and temporal confinement. However, ensemble-averaged detection typically conceals few-body effects. In this work, we characterize Coulomb correlations in laser-triggered electron number states generated at a Schottky field emitter in an ultrafast transmission electron microscope [7]. Based on an event-based detection scheme, we separate the state-averaged spectrum into the n-state components with a characteristic n-peak spectral shape. Furthermore, we identify a characteristic pair-correlation energy of around 2 eV. The strong inter-particle energy exchange is caused by acceleration-enhanced inter-particle Coulomb interaction, as confirmed by trajectory simulations. State-sorted beam caustics reveal a discrete increase in virtual source size, a longitudinal source shift, and a pronounced angular distribution of the few-electron states compared to single-electron pulses. The high fidelity of few-electron pulses in conjunction with single-particle detection enables the application of various experimental schemes typically employed in quantum optics. Specifically, we propose a scheme to generate an electron beam with sub- and super-Poissonian two-electron statistics. Applications of such beams include heralded single-electron sources and may foster new developments in free-electron quantum optics and quantum-enhanced electron microscopy.
Time
(Monday) 11:15 am - 12:00 pm
Event Details
John H. Gaida Affiliation: Max Planck Institute for Multidisciplinary Sciences and Georg August University of Göttingen (Germany) Research interests:
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John H. Gaida
Affiliation: Max Planck Institute for Multidisciplinary Sciences and Georg August University of Göttingen (Germany)
Research interests: Physics
Title: Attosecond electron microscopy using Lorentz PINEM and free-electron homodyne detection
Abstract: Transmission electron microscopy (TEM) offers high spatial resolution and is widely used to characterize optical ex citations and near fields by electron energy loss spectroscopy (EELS). This method probes self – induced electric fields in the nanostructure, using spontaneous inelastic scattering of electrons. Importantly, it is difficult to experimentally access near – fie ld phase information. Using external laser excitation, strong optical near fields can induce stimulated inelastic electron – light scattering, as employed in photon – induced near – field electron microscopy (PINEM). In this case, optical modes populated at the laser frequency are excited, providing enhanced spectral resolution and polarization sensitivity. Importantly, in this process, the induced near field is phase – locked to the exciting laser, which translates to a coherent phase modulation of the electron wa ve function. In this talk , we present two phase contrast techniques for imaging optical near fields at nanostructures. Specifically, we implement Lorentz – mode PINEM and free – electron homodyne detection (FREHD). Using these techniques, we image optical fields with subwave length (10 nm) spatial and sub – cycle temporal resolutions. Lorentz microscopy is an in – line holography technique, employing Fresnel diffraction at a small defocus. The electron wave function is locally mixed, and contrast arises near phase gradients. Sensitivity to the light field is obtained by energy filtering T EM (EFTEM) of PINEM – induced sidebands in the electron spectrum. We obtain complementary information about the phase profile by exploiting the conjugate symmetry of the energy gain and loss sidebands. From two complementary measurements, we reconstruct the light – imprinted phase using an iterative reconstruction algorithm. In the newly developed FREHD technique, on the other hand, we measure the phase profile by means of a phase – controlled reference interaction. The near field at a sample modulates the phase of the electron wavefunction. This wavefunction modulation is amplified or attenuated for in – phase and anti – phase reference interactions, respectively, which allows for a coherent read – out of a position – dependent phase. Overall, FREHD transfers concepts from homodyne detection in optics and amplitude (AM) and frequency modulation (FM) in radio techno logy to the realm of electron microscopy. Combining free electrons with phase – locked laser excitation offers fascinating new possibilities to image local attosecond and phase – resolved responses on the nanometer scale.
Time
(Monday) 11:15 am - 12:00 pm
august 2023
Event Details
Giorgio Sangiovanni Affiliation: Julius-Maximilians-Universität Würzburg Research Interests: condensed matter theory Title: Real-space Obstruction
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Giorgio Sangiovanni
Affiliation: Julius-Maximilians-Universität Würzburg
Research Interests: condensed matter theory
Title: Real-space Obstruction in Quantum Spin Hall Insulators
Abstract: In the hunt for room-temperature quantum spin Hall insulators, bismuthene [1] has demonstrated the impressive advantage of a local spin-orbit coupling experienced by the in-plane p-orbitals. This alternative to pi-bond graphene can be pushed to a conceptually even more essential level upon halving the honeycomb lattice, i.e. considering chiral p-orbitals on a triangular lattice [2]. Here, we theoretically conceive and experimentally realize for the first time a triangular QSHI, indenene, an indium monolayer exhibiting non-trivial valley physics and a large gap. We identify an interference mechanism of the Bloch functions and the emergence of a hidden honeycomb pattern in the charge localization, which makes the topological classification accessible to bulk experiments, without the necessity of quantum edge transport.
Time
(Saturday) 11:00 am - 12:00 pm
Event Details
Alessandro Toschi Affiliation: Institute of Solid State Physics (Technische Universität Wien) Research Interests: Theoretical Physics, Electronic Correlations,
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Alessandro Toschi
Affiliation: Institute of Solid State Physics (Technische Universität Wien)
Research Interests: Theoretical Physics, Electronic Correlations, Superconductivity, Quantum Criticality
Title: Local Moment Formation and Kondo screening from the Charge-Sector Perspective: How Perturbation Theory breaks down
Abstract: In this talk, I will discuss how the correct physical description of the formation of local moments and of their Kondo screening gets reflected in the charge-scattering sector. In particular, by a systematic analysis of the on-site charge and spin fluctuations on Hubbard atom, Anderson Impurity Model and Hubbard model solved by means of dynamical mean-field theory, I will demonstrate [1] how the strong intertwining between the different (spin and charge) sectors, which is crucial for a coherent description of correlated metallic and Mott insulating phases, necessarily drives the breakdown of the self-consistent perturbation expansion [1,2].
The improved understanding of the frequency structures of the two-particle correlation functions has also allowed us [2] to identify the typical fingerprints of the Kondo physics in the charge sector and, on an even more quantitative level, to introduce a new, quite accurate criterion for estimating the Kondo temperature. Interestingly, the same scattering processes responsible for the on-site charge localization may result in an effective electronic attraction [3,4], triggering the phase-separation instabilities emerging in the proximity of Mott-Hubbard or Hund’s-Mott metal-insulator transitions.
Time
(Saturday) 10:00 am - 11:00 am
Event Details
Pascal Ruffieux Affiliation: Swiss Federal Laboratories for Materials Science and Technology Research Interests: nanographene, graphene nanoribbon, surface science
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Pascal Ruffieux
Affiliation: Swiss Federal Laboratories for Materials Science and Technology
Research Interests: nanographene, graphene nanoribbon, surface science
Title: On-surface synthesis of magnetic nanographenes
Abstract: Recent progress in the on-surface synthesis of nanographenes has given access to an extremely rich materials class where physical properties can be tuned in a wide range. The most prominent nanographenes include armchair graphene nanoribbons (GNRs) with width-dependent electronic band gaps [1], zigzag GNRs with spin-polarized edge states [2] and width-modulated GNRs hosting tunable topological bands [3]. Most recently, the successful synthesis of a series of open-shell nanographenes with magnetically nontrivial ground states has catapulted carbon-based magnetism to a new level. The basic concept followed here is realization of sublattice-imbalanced or topologically frustrated nanographenes hosting unpaired electrons. A deterministic realization of such nanographenes is achieved through a combined solution on and on-surface synthesis approach. Here, I will report recent advances in the on-surfaces synthesis of nanographenes with chemically tuned magnetic interaction strength between unpaired electrons in diradical nanographenes [4]. The controlled combination of different magnetic nanographenes allows formation of both, antiferromagnetically and ferromagnetically coupled dimers and trimers based on spin-½ and spin-1 molecular building blocks as well as extended spin chains [5]. Here, we investigate the length and site-dependent spin excitations with inelastic scanning tunneling spectroscopy and compare them theoretical predictions on spin-1 chains and confirm Haldane gap and fractional edge excitations for open chains. As an extension of the on-surface synthesis approach, we recently achieved successful formation of open-shell nanographenes using scanning tunneling microscopy tip-based activation of hydrogen-protected precursors [6,7]. This has the advantage that magnetic nanographenes can be prepared and characterized on a larger range of substrates since no specific catalytic substrate properties are needed here.
Time
(Friday) 2:00 pm - 3:00 pm
Event Details
Andreas Osterwalder Affiliation: Ecole Polytechnique Federale de Lausanne (EPFL) Research Interests: Physics Title:
Event Details
Andreas Osterwalder
Affiliation: Ecole Polytechnique Federale de Lausanne (EPFL)
Research Interests: Physics
Title: From cold gas-phase stereodynamics to kinetics at water-water interfaces
Abstract: I will briefly introduce the two primary research directions covered in our group:
A first part will be on experiments to study sub-Kelvin stereodynamics in merged beams. We investigate prototypical energy transfer reactions in the gas phase, namely between metastable Ne(3P2) and other rare gas atoms or small molecules. Such reactions can proceed along two pathways according to NeX+ + e ̄← Ne(3P2) + X → Ne(1S) +X+ + e ̄ called Penning ionization (producing X+) and associative ionization (producing NeX+), respectively. At high energies the branching ratio between these channels can be controlled through the orientation of the Ne(3P2) atom, but this ability is lost at low energies due to a reorientation of the reactants. In the second part I will be describing our efforts towards studies of gas — liquid water scattering dynamics, for which we cross a molecular beam with a liquid water flat-jet. Liquid flat-jets can be produced by impinging two cylindrical microjets at controlled angles and flow-rates. Such an arrangement produces a series of drop-shaped leaves that provide a flat surface from which gas-phase molecules can be scattered. But, as will be shown, the first leaf in this chain can also serve as a tool to prepare a controlled interface between two liquids, possible miscible, an arrangement that is ideally suited for the study of chemical kinetics at liquid-liquid interfaces.
Time
(Friday) 2:20 pm - 2:50 pm
Event Details
Wilson Ho Affiliation: University of California, Irvine Date: Aug 16th (Wed), 2023 (17:00 - 18:00, KST) (10:00 -11:00, CET) Title: A Qubit-Based Quantum Microscope for
Event Details
Wilson Ho
Affiliation: University of California, Irvine
Date: Aug 16th (Wed), 2023 (17:00 – 18:00, KST) (10:00 -11:00, CET)
Title: A Qubit-Based Quantum Microscope for Space-Time Sensing
Abstract: In contrast to all other microscopes, a qubit-based quantum microscope (QM) combining coherent light with the scanning tunneling microscope (STM) is unique in incorporating the quantum superposition principle in its operation. This QM uses the superposition of two levels in a single hydrogen molecule as the sensor to probe the electric fields of a sample’s surface. In a pilot study (Science 376, 401, 2022; Phys. Rev. Lett. 130, 096201, 2023) the QM demonstrates a 300-fold finer energy resolution and 0.1 angstrom spatial sensitivity of the sample’s near-field electrostatics, compared to microscopes not based on this quantum principle. Furthermore, the wave-particle duality, nonlinear Stark effects, superposition of multiple quantum states, and entanglement among adjacent two levels illustrate the sensitivity of the QM to a set of basic phenomena underlying quantum mechanics. This qubit-based QM advances precision measurement with space-time resolution by irradiating the STM junction with femtosecond THz radiation and recording in the time domain coherent oscillations of the light-induced rectified tunneling current. The common occurrence of systems with two levels within a double-well potential suggests a broad application of the QM in probing the heterogeneous distribution of static and dynamic properties of electrons in functional materials.
To participate in the talk, please, fill out the Registration Form →
Time
(Wednesday) 5:00 pm - 6:00 pm (KST)
Location
Center for Quantum Nanoscience
Research Cooperation Building,52 Ewhayeodae-gil, Daehyeon-dong
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Alec Wodtke Affiliation: Max Planck Institute for Multidisciplinary Sciences Date: Aug 11th (Fri), 2023 (17:00 - 18:00, KST) (10:00 -11:00, CET) Title: Condensed phase tunneling
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Alec Wodtke
Affiliation: Max Planck Institute for Multidisciplinary Sciences
Date: Aug 11th (Fri), 2023 (17:00 – 18:00, KST) (10:00 -11:00, CET)
Title: Condensed phase tunneling from Enzyme Kinetics to Astrochemistry
Abstract: Superconducting nanowire single-photon detectors (SNSPDs) provide sufficient sensitivity to enable laser-induced fluorescence (LIF) experiments in the mid-infrared, an exciting technical development for studying molecule-surface interactions. In this talk, I will present results of experiments on the vibrational dynamics of monolayers and multilayers of solid CO adsorbed at the surface of a NaCl crystal that provide observations of quantum state resolved dynamics. When, for example, a pulsed ns laser excites CO to its v=1 state, a monochromator equipped with an SNSPD detects wavelength- and time-resolved mid-infrared emission from CO vibrational states up to v=27 that are produced by vibration-vibration (V-V) energy transfer. Kinetic Monte Carlo (kMC) simulations show that vibrational energy collects in a few CO molecules at the expense of those up to eight lattice sites away. The excited CO molecules relax by a mechanism resembling Sommerfeld’s theory of ground waves important to radio wave propagation, losing their energy to NaCl lattice-vibrations via the electromagnetic near-field. This is a weak coupling limit, where the potential energy surface is not needed to describe the relaxation process.
At high resolution, we observe new lines appearing in the infrared emission spectra, showing that CO vibrational energy converts “the right side up” where CO is bound by its C-atom to the surface to an “upside down” metastable isomer. Flipping back involves thermally activated tunneling, exhibiting a large isotope effect, where the lightest isotope is not the fastest tunneller. This is explained by a quantum rate theory of isomerization involving tunneling gateways. Near resonant states, localized on opposite sides of the isomerization barrier are coupled by collisions with a phonon bath. This represents an alternative to traditional tunneling pictures like Instanton and WKB, which are based on continuum scattering picture that is not valid in condensed phases.
*Arnab Choudhury 1,2, Jessalyn Devine 1, Dirk Schwarzer 1, Shreya Sinha 3, Peter Saalfrank 3, Alec Wodtke 1,2 1 Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany 2 Institute for physical chemistry, University of Göttingen, Göttingen, Germany 3 University of Potsdam, Potsdam Germany See Choudhury et al., Nature 612, 691–695 (2022)
To participate in the talk, please, fill out the Registration Form →
Time
(Friday) 5:00 pm - 6:00 pm (KST)
Location
Center for Quantum Nanoscience
Research Cooperation Building,52 Ewhayeodae-gil, Daehyeon-dong
Event Details
Claudiu Genes Academic Affiliation: Max Planck Institute for the Science of Light Research Interests: Quantum optics, Molecular quantum technologies, Quantum information, Quantum
Event Details
Claudiu Genes
Academic Affiliation: Max Planck Institute for the Science of Light
Research Interests: Quantum optics, Molecular quantum technologies, Quantum information, Quantum sensing, Organic opto-electronics, Cooperative quantum phenomena, Quantum metrology, Quantum optomechanics, Energy and charge transport
Title: Quantum optics with molecules
Abstract: Theoretical tools of quantum optics, such as the master equation and the quantum Langevin equations approaches, are ideally suited to treat the dynamics of complex open quantum systems. A reduction to basic ingredients has seen such methods successfully applied to ensembles of two level quantum emitters, where the electronic degree of freedom is interfaced with single or multimode quantum light. Standard aspects tackled within this formalism include free space cooperative effects such as super – and subradiance (radiative emission rates larger or smaller than that of an isolated individual system) and cavity quantum electrodynamics effects such as strong coupling, polariton physics or Purcell enhancement of spontaneous emission rates.
Time
(Monday) 11:00 am - 12:00 pm
july 2023
Event Details
Duck-Ho Kim Affiliation: Korea Institute of Science and Technology (KIST) Research interests: Spintronics Title:
Event Details
Duck-Ho Kim
Affiliation: Korea Institute of Science and Technology (KIST)
Research interests: Spintronics
Title: Spin Transport and Dynamics in Ferrimagnetic Materials
Abstract: The dynamic phenomena of topological spin objects in magnetic materials have been actively studied not only for their academic interest but also for their potential applications in next – generation memory devices [1 – 4]. Representative topological spin objec ts include chiral magnetic domain walls [1, 2] and magnetic skyrmions [3, 4]. It is possible to manipulate topological spin objects using electric current, and the underlying mechanism involves the conservation of angular momentum arising from the interact ion between the electron’s spin and the spin of the phase spin structure as the electron traverses the magnetic material [5, 6]. This interaction is known as spin torque and can be divided into spin – transfer torque and spin – orbit torque depending on the tr ansmitting materials . Recently, ultrafast motion of topological spin objects has been predicted in antiferromagnetic materials (total magnetization = 0) through theoretical studies [7]. Unfortunately, antiferromagnetic materials are difficult to measure (t otal magnetization = 0) and challenging to control (due to strong coupling energy), making it difficult to experimentally verify the theory. However, in the case of ferrimagnetic materials, which have a finite magnetization at the angular momentum compensa tion point where the angular momentum is zero, it has been possible to investigate the spin dynamics of antiferromagnetic materials. With this possibility, ultrafast motion has been observed at the angular momentum compensation point when topological spin objects are driven by a magnetic field [8]. In this presentation, we will discuss the spin transfer torque phenomenon [9] and the phenomenon of skyrmion hall effect [10] at the angular momentum compensation point when topological spin structures is driven by electric current in ferrimagnetic materials
Time
(Thursday) 11:00 am - 12:00 pm
14jul11:00 am12:00 pmWoo-Joong KimSeattle University11:00 am - 12:00 pm KST
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Woo-Joong Kim Affiliation: Professor of Physics, Seattle University Research interests: Precision force measurements, Casimir and van der Waals
Event Details
Woo-Joong Kim
Affiliation: Professor of Physics, Seattle University
Research interests: Precision force measurements, Casimir and van der Waals forces, surface patch effect, quantum conductance in nanowire
Title: An optically-driven macroscopic cantilever
Abstract: I will report an interferometric experiment to detect optically-driven resonance on a macroscopic object. Utilizing dynamic force microscopy, the resonant motion of a cm-sized cantilever driven by an amplitude-modulated laser is directly observed. I will also discuss other experimental techniques underway in our research lab and their potential applications to precision measurements such as tests of short-range gravity.
Time
(Friday) 11:00 am - 12:00 pm
june 2023
Event Details
Sungkyun Choi Affiliation: Center for Integrated Nanostructure Physics IBS, SungKyunKwan University Research interests: Quantum Spin Liquids, Multiferroics,
Event Details
Sungkyun Choi
Affiliation: Center for Integrated Nanostructure Physics IBS, SungKyunKwan University
Research interests: Quantum Spin Liquids, Multiferroics, Topology in Magnetism, Quantum Phase Transitions
Title: Spectroscopy on Quantum Magnetism
Abstract: In this seminar, we will introduce how spectroscopy can be utilized in understanding contemporary research topics in condensed matter physics, in which quantum magnetism plays an important role. To this end, our primary experimental technique is neutron spectroscopy, complemented by X – ray and Raman spectroscopy. Case examples such as quantum spin liquids, multiferroics, and insulator – metal transitions will be discussed.
Time
(Thursday) 11:00 am - 12:00 pm
20jun11:00 am12:00 pmPierre JosseUniversity of Angers, Yonsei University11:00 am - 12:00 pm KST
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Pierre Josse Affiliation: University of Angers, Yonsei University Research interests: Organic Chemistry, Dye Chemistry, Organic Electronics Title:
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Pierre Josse
Affiliation: University of Angers, Yonsei University
Research interests: Organic Chemistry, Dye Chemistry, Organic Electronics
Title: Tailoring π-conjugated molecular and macromolecular systems for addressing specific needs and requirements: from organic photovoltaics to theranostics
Abstract: Active materials for organic electronic applications such as solar cells or light emitting diodes usually requires strong absorbers and/or emitters in the visible/NIR range. Over the last 30 years, researchers around the world have been developing new materials, optimizing devices and rationalizing structures/properties relationships to demonstrate the interest of these technologies and potentially bring them on the market. The rapid growth of organic electronics was then closely related to the capacity of synthetic chemists to generate new and original molecular and macromolecular structures . With the only limitation being basically the imagination, organic synthesis indeed offers countless reactivities, tools and possibilities to afford functional compounds with specific properties. As a chemist specialized in π-conjugated systems, I’ll thus cover, through this presentation, projects and strategies developed to address specific needs and requirements for practical applications ranging from organic photovoltaics to light emitting devices and even photosensitizers for theranostic applications.
Time
(Tuesday) 11:00 am - 12:00 pm
16jun11:00 am12:00 pmVasily KravtsovITMO University11:00 am - 12:00 pm KST
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Vasily Kravtsov Affiliation: ITMO University Research interests: Two-dimensional quantum materials, ultrafast spectroscopy, nonlinear nano-optics Title:
Event Details
Vasily Kravtsov
Affiliation: ITMO University
Research interests: Two-dimensional quantum materials, ultrafast spectroscopy, nonlinear nano-optics
Title: Near-field spectroscopy and control of excitons in 2D van der Waals heterostructures.
Abstract: Atomically thin transition metal dichalcogenides (TMDs) are direct band gap semiconductors that host excitons with large binding energies and sizeable exciton – exciton interaction strength. When stacked into heterostructures, these materials acquire many unique optical properties associated with the interlayer coupling and formation of new excitonic and polaritonic states. Near – field spectroscopy provides an indispensable tool for studying such states, as well as their coupling, dynamics, and control. I w ill present results of our recent investigation of excitonic effects in van der Waals heterostructures via different near – field spectroscopy implementations including tip – enhanced spectroscopy and spectroscopy in the Fourier plane via evanescent wave coupling through a solid immersion lens. First, I will discuss the possibility of controlling the intralayer and interlayer excitons within a nanoscopic volume of TMD heterobilayers. Second, I will discuss experiments on probing and controlling exciton – polarito ns in all van-der-Waals heterostacks in the strong light-matter coupling regime.
Time
(Friday) 11:00 am - 12:00 pm
08jun10:00 am11:30 amPaul WeissUniversity of California, Los Angeles, USA10:00 am - 11:30 am KST
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Paul Weiss Academic Affiliation: University of California, Los Angeles (UCLA) Research interests: Nanoscience, Chemistry, Physics, Nanotechnology, Biotechnology Title: Understanding and
Event Details
Paul Weiss
Academic Affiliation: University of California, Los Angeles (UCLA)
Research interests: Nanoscience, Chemistry, Physics, Nanotechnology, Biotechnology
Title: Understanding and Controlling Charge, Heat, and Spin at Atomically Precise Interfaces
Abstract: One of the key advances in nanoscience and nanotechnology has been our increasing ability to reach the limits of atomically precise structures. By having developed the “eyes” to see, to record spectra, and to measure function at the nanoscale, we have been able to fabricate structures with precision as well as to understand the important and intrinsic heterogeneity of function found in these assemblies. The physical, electronic, mechanical, and chemical connections that materials make to one another and to the outside world are critical. Just as the properties and applications of conventional semiconductor devices
depend on these contacts, so do nanomaterials, many nanoscale measurements, and devices of the future. We explore the important roles that these contacts can play in preserving key transport and other properties. Initial nanoscale connections and measurements guide the path to future opportunities and challenges ahead. Band alignment, minimally disruptive connections, and control of spin and heat are all targets and can be characterized in both experiment and theory. I discuss our initial forays into this area in a number of materials systems.
Time
(Thursday) 10:00 am - 11:30 am
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Ruslan Temirov Academic Affiliation: Peter Grunberg Institute, Forschungszentrum Jülich Research interests: Scanning Probe Microscopy, Cryogenics
Event Details
Ruslan Temirov
Academic Affiliation: Peter Grunberg Institute, Forschungszentrum Jülich
Research interests: Scanning Probe Microscopy, Cryogenics
Time
(Wednesday) 3:00 pm - 4:00 pm
Event Details
Kyoung-Duck Park Academic Affiliation: Pohang University of Science and Technology (POSTECH) Research interests: Physics Title: Tip-enhanced cavity-spectroscopy
Event Details
Kyoung-Duck Park
Academic Affiliation: Pohang University of Science and Technology (POSTECH)
Research interests: Physics
Title: Tip-enhanced cavity-spectroscopy
Time
(Friday) 2:00 pm - 3:00 pm
may 2023
Event Details
Philip Kim Affiliation: Harvard University Date: May 17, 2023 (15:00 - 16:00, KST; Wednesday) (8:00, CET; Wednesday) (23:00, PDT; Tuesday) Title: Engineered quantum materials using
Event Details
Philip Kim
Affiliation: Harvard University
Date: May 17, 2023 (15:00 – 16:00, KST; Wednesday) (8:00, CET; Wednesday) (23:00, PDT; Tuesday)
Title: Engineered quantum materials using van der Waals atomic layer heterostructures
Abstract:
Over the last 50 years, two-dimensional (2D) electron systems have served as a key material platform for the investigation of fascinating quantum phenomena in engineered material systems. Recently, scientists have found that it is feasible to produce van der Waals (vdW) layered materials that are atomically thin. In these atomically thin materials, quantum physics enables electrons to move effectively only in a 2D space. Additionally, by stacking these 2D quantum materials, it is also possible to create atomically thin vdW heterostructures with an extensive range of interfacial electronic and optical properties. Novel 2D electronic systems realized in vdW atomic stacks have served as an engineered quantum material platform. In this presentation, we will discuss several research initiatives aimed at realizing emergent physical phenomena in stacked vdW interfaces between 2D materials.
To participate in the talk, please, fill out the Registration Form →
Time
(Wednesday) 3:00 pm - 4:00 pm (KST)
Location
Center for Quantum Nanoscience
Research Cooperation Building,52 Ewhayeodae-gil, Daehyeon-dong
march 2023
31mar2:00 pm3:30 pmMaria SpethmannUniversity of Basel2:00 pm - 3:30 pm KST
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Maria Spethmann Affiliation: University of Basel Title: High-fidelity two-qubit gates of hybrid superconducting-semiconducting singlet-triplet qubits Abstract: Hybrid systems comprising superconducting and
Event Details
Maria Spethmann
Affiliation: University of Basel
Title: High-fidelity two-qubit gates of hybrid superconducting-semiconducting singlet-triplet qubits
Abstract:
Hybrid systems comprising superconducting and semiconducting materials are promising architectures for quantum computing. Superconductors induce interactions between the spin degrees of freedom of semiconducting quantum dots, based on crossed Andreev processes. In the talk I will present our theory where we show that these interactions are widely anisotropic when the semiconductor material has strong spin-orbit interactions. This anisotropy is tunable and enables fast and high-fidelity two-qubit gates between singlet-triplet spin qubits. The reason is that the design is immune to leakage into non-computational states and removes always-on interactions between the qubits (crosstalk). We estimate two-qubit gate fidelities exceeding 99.9% without fine-tuning of parameters.
Time
(Friday) 2:00 pm - 3:30 pm
february 2023
Event Details
Nicolas Lorente Affiliation: CFM – Materials Physics Center Date: Feb 28th, 2023 (17:00 - 18:00, KST) (09:00 -10:00, CET) Title: The Kondo effect as revealed
Event Details
Nicolas Lorente
Affiliation: CFM – Materials Physics Center
Date: Feb 28th, 2023 (17:00 – 18:00, KST) (09:00 -10:00, CET)
Title: The Kondo effect as revealed by STM measurements
Abstract:
The ground state of a metal is, to a great degree of accuracy, well described by one-electron states. However, as soon as there is a magnetic interaction that can change the spin of the electrons, the ground state becomes a very complex state. The reason for this is the development of a multielectronic state that cannot be separated in single states. Magnetic impurities are efficient at mixing electronic spins and the new emerging ground state is the hallmark of the Kondo effect. To this respect, the scanning tunneling microscope (STM) is an excellent tool to interrogate the electronic correlations induced by the magnetic impurities. It can locally study the magnetic impurities on metallic substrate and it can reveal the properties of the electronic states essential for the Kondo state [1]. In this Colloquium, I will review the main features of the Kondo effect and how they have been revealed by STM experiments. Moreover, I will analyze some recent results obtained in my group in collaboration with experimental colleagues. In the spirit of a Colloquium talk, the exposition will be pedagogical, emphasizing physical results over formal theoretical considerations.
The first case will be the study of Manganese phthalocyanines on different metallic substrates. Manganese phathalocyanines are S=3/2 magnetic molecules that present orbital and spin degeneracies. Here, the Kondo effect is efficiently mixed with orbital excitations [2]. The second topic will be about Nickelocene molecules that are also magnetic, but their ground state is S=1 and the Kramers theorem does not apply. The spin degeneracy is lifted and no Kondo effect is detectable and instead spin-flip excitations are strong signals in the experimental spectra [3]. In this case, the competing excitations are vibrations. The joint Kondo plus vibrational excitation reveal some astonishing features [4]. Finally, even in the case of a pure S=1/2 cobaltocene molecule, the Kondo spectra becomes strongly modified by the presence of molecular vibrations [5].
References :
[1] D.-J. Choi and N. Lorente, Handbook of Materials Modeling: Applications: Current and Emerging Materials, p. 467, Springer International Publishing (2020).
[2] Jens Kügel et al. Phys. Rev. Lett. 121, 226402 (2018)
[3] Benjamin Verlhac et al. Science 366, 623 (2019)
[4] Nicolas Bachelier et al. Nature Comm. 11, 1619 (2020)
[5] Léo Garnier et al. Nano Letters 20, 8193 (2020).
To participate in the talk, please, fill out the Registration Form →
Time
(Tuesday) 5:00 pm - 6:00 pm (KST)
Location
Center for Quantum Nanoscience
Research Cooperation Building,52 Ewhayeodae-gil, Daehyeon-dong
09feb10:00 am11:30 amDaniel Kyungdeock ParkYonsei University10:00 am - 11:30 am KST
Event Details
Daniel Kyungdeock Park Academic Affiliation: Yonsei University Title: Quantum machine learning: opportunities and challenges Abstract: Quantum computing
Event Details
Daniel Kyungdeock Park
Academic Affiliation: Yonsei University
Title: Quantum machine learning: opportunities and challenges
Abstract:
Quantum computing has the potential to outperform any foreseeable classical computers for solving certain computational problems. With the growing demand for advanced computing power and methods in big data and artificial intelligence, quantum machine learning (QML) has emerged as one of the most exciting applications of quantum computing. In its early developments, QML gathered much attention mainly due to the quantum algorithm that solves the system of linear equations exponentially faster than its classical counterpart. However, this algorithm requires a fault-tolerant quantum computer and a quantum random access memory, which remain long-term prospect. Thus an important and challenging question is how noisy intermediate-scale quantum (NISQ) computers that are within reach can be utilized for QML. In this talk, I will first briefly introduce quantum machine learning. Then I will present several QML approaches that aim to utilize NISQ to the full extent and attain quantum advantages in the near future.
Time
(Thursday) 10:00 am - 11:30 am
Event Details
Joseph A Stroscio Title: Unraveling Quantum Geometry and Orbital Magnetism Contributions to Landau Levels in Moiré Superlattices Abstract: Flat and narrow
Event Details
Joseph A Stroscio
Title: Unraveling Quantum Geometry and Orbital Magnetism Contributions to Landau Levels in Moiré Superlattices
Abstract:
Flat and narrow band physics in moiré quantum matter (MQM) has proven to be extremely rich with new emergent quantum phases which can be tuned with applied electric and magnetic fields. The topological properties of the eigenstates of the moiré Hamiltonian are critical for establishing the quantum phase of the system. While the emergence of non-trivial Chern numbers has been observed, it is important to characterize the quantum geometry in detail including the Berry curvature and the less known quantum metric effects which give rise to orbital magnetism in these systems. For almost a century, magnetic oscillations have been a powerful “quantum ruler” for measuring Fermi surface topology. In this presentation, I show the use of a quantum ruler of Landau levels via scanning tunneling spectroscopy to probe quantum geometry and topology in twisted double bilayer graphene (TDBG) [1]. The high-resolution Landau level spectra reveal tunable electron- and hole-like pockets that deviate significantly in their magnetic response from the semiclassical Onsager relation. A quantitative analysis of the Landau levels demonstrates the significance of quantum geometry contributions to the magnetic energy levels, highlighting the effect of the tunable Berry curvature and local orbital magnetism. The deviation from semiclassical behavior is due to the higher order magnetic field response of TDBG, which in turn is related to the quantum geometry of the electronic structure. The first-order correction in magnetic field, interpreted as an orbital magnetic moment, manifests as a valley splitting of the Landau levels. The second-order correction—orbital magnetic suscepti
1Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
Time
(Thursday) 1:30 pm - 3:00 pm
december 2022
14dec1:30 pm3:00 pmClément CabanetosUniversity of Angers1:30 pm - 3:00 pm KST
Event Details
Clément Cabanetos Academic Affiliation: University of Angers Title: “Sooner or later, everything old is new again”: Functionalization and use of a forgotten
Event Details
Clément Cabanetos
Academic Affiliation: University of Angers
Title: “Sooner or later, everything old is new again”: Functionalization and use of a forgotten dye
Abstract:
Abstract: Since the advent of organic electronics, various classes of π-conjugated molecular and macromolecular semiconductors have been reported. Among them, imide-containing rylenes have attracted considerable research attention due to their redox, electron-withdrawing and charge-carrier transport properties, as well as their excellent chemical, thermal, and photochemical stabilities. Naphthalene diimide (NDI) and perylene diimide (PDI) can be unequivocally recognized as the most studied imide based building blocks for the preparation of high-performance electron transporting optoelectronic materials. Within these wide-ranging studies, considerable effort has been undertaken to functionalize both the bay positions and the nitrogen atom constituting the imide group (N-positions) to bring solubility, tune the molecular (opto)electronic characteristics, and build extended π-conjugated architectures. Despite interesting fluorescent properties, the N-(alkyl)benzothioxanthene-3,4-dicarboximide (BTI), a sulfur containing rylene-imide dye, has not yet triggered such interest. Exclusively functionalized on the N-position for imaging and staining applications, we recently focused our attention in functionalizing the p-conjugated core of this forgotten dye for the preparation of new and original materials for organic electronics, but not only…
Clément Cabanetos: clement.cabanetos@cnrs.fr
After graduation in 2008, Clément Cabanetos undertook a PhD at the CEISAM laboratory (Nantes, France) on the synthesis of new crosslinkable polymers for nonlinear optical applications. Shortly after his thesis defense, he joined the group of Jean Fréchet (KAUST, (Saudi Arabia) as a postdoctoral fellow to prepare efficient π-conjugated macromolecular materials for organic photovoltaics. In 2013, he was recruited as a permanent CNRS researcher and joined the MOLTECH-Anjou laboratory in Angers to develop new and original concepts for organic electronics. He then defended his habilitation in 2018 (associate professorship) and received in 2019 the CNRS bronze medal that awards young and promising researchers. Recently (august 2021) he moved to Seoul in a joint French (CNRS)-Korean International laboratory (2BFUEL) hosted by the Yonsei University where he was promoted director in September 2022.
Time
(Wednesday) 1:30 pm - 3:00 pm
Event Details
Harald Brune Affiliation: École Polytechnique Fédérale de Lausanne (EPFL) (Swiss Federal Institute of Technology Lausanne) Date: Dec 7th, 2022 (17:00 KST; 09:00 CET) Title: Exploring
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Harald Brune
Affiliation: École Polytechnique Fédérale de Lausanne (EPFL) (Swiss Federal Institute of Technology Lausanne)
Date: Dec 7th, 2022 (17:00 KST; 09:00 CET)
Title: Exploring the Magnetic Quantum States of Single Surface Adsorbed Atoms
Abstract:
The magnetic properties of single surface adsorbed atoms became one of the core interests in surface and nanoscience in 2003, where single Co atoms on Pt were reported to have 200 times the magnetic anisotropy energy of bulk Co [1]. Years later, even 1000 times this energy was reached for single Co atoms on thin MgO films [2]. In a classical picture, this suggests that these single atoms should be rather stable magnets. However, despite numerous efforts, the magnetic quantum states of all investigated single surface adsorbed transition metal atoms had very short magnetic relaxation times, below 1 µs.
Immediately after changing to rare-earth atoms, a few adsorbate/substrate combinations could be identified, where the magnetization vector of a single atom is indeed stable over hours in the absence of an external magnetic field [3,4]. Therefore, these systems are single atom magnets and enable magnetic information storage in the smallest unit of matter. We will give an overview over the present adsorbate/substrate systems exhibiting single atom magnet behavior [3 – 7] and explain the essential ingredients for this surprising stability of single spin systems that are exposed to numerous perturbations from the environment. These atoms can be placed very close and still individually be addressed conceptually enabling information storage at densities by 3 orders of magnitude larger than presently used devices.
Now the fundamental research field turns its attention to quantum coherent spin operations in single surface adsorbed atoms. If they have long enough coherence times with respect to the time it takes to perform a single quantum spin operation, these would be single atom quantum bits. The requirements for long coherence times of the magnetic quantum states are quite different from the ones of magnetic relaxation times. We will illustrate this with a few examples and point out single rare-earth atom systems that lend themselves already now as quantum repeaters in telecommunication [8], creating hope that single atom qubits may indeed become reality in the near future.
[1] P. Gambardella et al. Science 300, 1130 (2003).
[2] I. G. Rau et al. Science 344, 988 (2014).
[3] F. Donati et al. Science 352, 318 (2016).
[4] R. Baltic et al. Nanolett. 16, 7610 (2016).
[5] A. Singha et al. Nat. Communic. 12, 4179 (2021).
[6] F. Donati et al. Nano Lett. 21, 8266 (2021).
[7] V. Bellini et al. ACS Nano 16, 11182 (2021).
[8] M. Zhong et al. Nature 517, 177 (2015).
To participate in the talk, please, fill out the Registration Form →
Time
(Wednesday) 5:00 pm - 6:00 pm (KST)
Location
Center for Quantum Nanoscience
Research Cooperation Building,52 Ewhayeodae-gil, Daehyeon-dong
Event Details
Pavel Jelinek Academic Affiliation: Institute of Physics of the Czech Academy of Sciences (FZU) Title: Quinone-based 1D molecular chains on surfaces: magnetism
Event Details
Pavel Jelinek
Academic Affiliation: Institute of Physics of the Czech Academy of Sciences (FZU)
Title: Quinone-based 1D molecular chains on surfaces: magnetism and nuclear quantum effects
Abstract:
Low dimensional materials offer very interesting material and physical properties due to reduced dimensionality. At present, 2D materials are the focus of attention. However, 1D systems often show far more exotic behavior due to reduced dimensionality enhancing substantially quasiparticle interactions. However, synthesis of purely 1D molecular systems still remains elusive. In this talk, we will explore on-surface chemistry using 2,5-diamino-1,4-benzoquinonediimines (2HQDI) precursor [1], which offers interesting playground for growing molecular chains of distinct chemical character.
In first part of the talk, we will present formation of hydrogen-bonded 2HQDI molecular chains on Au(111) surface. We will discuss a significant influence of nuclear quantum effects on structural, mechanical and electronic properties of these 2HQDI molecular chains. Namely, we demonstrate that the presence of concerted proton motion not only enhances significantly the cohesive energy of intermolecular hydrogen bonds but it also causes emergence of new electronic states located at the edges [2].
In the second part, we introduce on-surface synthesis of 1D coordination p-d conjugated polymers, achieved by co-deposition of 2HQDI molecular precursor and various transition metals (Fe, Co, Ni, Cr, Cu) atoms on metal surfaces under UHV conditions [3]. This route results in formation of flexible coordination polymers with length up to hundreds of nanometers. We characterize physical and chemical properties by means of low temperature UHV scanning probe microscopy supported by theoretical simulations. We will discuss distinct coordination of transition metal and corresponding atomic, electronic and magnetic structure [4]
Finally, we will demonstrate fully reversible multiconfigurational light-driven spin crossover switches in a single p-d organometallic Co-QDI chain suspended between two electrodes. The external light enables us to realize reversible spin cross over between low and high-spin states of individual cobalt centers within the chain.
[1] O. Siri, et al J. Am. Chem. Soc. 125, 13793 (2003).
[2] A. Cahlik et al ACS Nano 15, 10357 (2021).
[3] V.M. Santhini et al, Angew. Chem. Int. Ed. 60, 439 (2021).
[4] Ch. Wackerlin et al, ACS Nano (2022) DOI: 10.1021/acsnano.2c05609
Time
(Tuesday) 10:00 am - 11:30 am
november 2022
Event Details
Wolf-Dieter Schneider Academic Affiliation: Ecole Polytechnique Fédérale de Lausanne (EPFL) Title: A short history of spectroscopic manifestations of the Kondo effect Abstract: In 1930,
Event Details
Wolf-Dieter Schneider
Academic Affiliation: Ecole Polytechnique Fédérale de Lausanne (EPFL)
Title: A short history of spectroscopic manifestations of the Kondo effect
Abstract:
In 1930, a resistance minimum observed in dilute magnetic alloys was the first experimental evidence for a new scattering mechanism of conduction electrons at magnetic impurities at low temperatures. More than 30 years later J. Kondo developed a theory that describes the effect as a consequence of the spin-flip scattering of conduction electrons at a localized magnetic impurity: The term “Kondo effect” was born for this phenomenon. About the same time P. W. Anderson developed his “single impurity model” where he calculated the implications of this scattering mechanism for the local density of states:
He found a strong singularity at the Fermi level, termed “Kondo resonance”. This prediction triggered numerous experimentalists to search and find this resonance in rare earth and transition metal alloys with techniques such as point contact measurements, photoelectron, and scanning tunneling spectroscopies (STS).
The latter technique enabled us to study the manifestations of the Kondo effect for individual atoms and molecules adsorbed on surfaces. An interesting case are the rare earth atoms. Their magnetic moment originates from electrons in the partially filled 4f orbitals which are well shielded by the outerlying orbitals leading to a very weak hybridization between them and the localized 4f electron. This is most probably the reason, why so far no Kondo resonance has been detected for a single Ce adatom on metallic and insulating surfaces. The Ce adatom remains spectroscopically “dark”. However, here we show that we can detect the magnetic moment of an individual Ce adatom adsorbed on a Cu2N ultra thin film on Cu(100) by using a sensor tip that has its apex functionalized with a Kondo screened spin system, a small Ce-cluster. We calibrate the sensor tip by deliberately coupling it to a well characterised Fe surface atom. Subsequently we use the splitting of the tip’s Kondo resonance when approaching a spectroscopically dark Ce atom to sense its magnetic moment [1]. Thus, the functionalized tip is used as a spin detector for single magnetic Ce-adatoms in the absence of an external magnetic field. This achievement indicates an alternative route to the study of magnetic nanostructures circumventing the application of spin-polarized STM tips.
When Ce-atoms self-assemble to create a superlattice on Ag(111) with an interatomic
lattice spacing of 3.2 nm [2], a Kondo lattice is formed. The differential conductance spectra
obtained on single Ce-adatoms within the superlattice reveal a considerably broadened Kondo
resonance as compared to the one of about 1 meV found for isolated Ce-clusters. This observation might indicate the presence of antiferromagnetic indirect exchange interactions (RKKY) in the superlattice. Depending on the distance between the Ce-adatoms in the superlattice the competition between Kondo singlet formation and RKKY interaction may lead to a coherent antiferromagnetic or ferromagnetic state when passing through a quantum critical point. Future studies at lower temperatures and with higher spectroscopic
resolution may provide new insights into the interplay between Kondo physics, localized spin-flip excitations, and the magnetic exchange interaction.
[1] M. Ternes, C. P. Lutz, A. J. Heinrich, and W.-D. Schneider, Phys. Rev. Lett. 124, 167202 (2020)
[2] F. Silly, M. Pivetta, M. Ternes, F. Patthey, J. P. Pelz, and W.-D. Schneider, Phys. Rev. Lett. 92, 016101 (2004)
Time
(Thursday) 10:00 am - 11:30 am
01nov3:00 pm4:00 pmHan-woong YeomCALDES, IBS & POSTECH3:00 pm - 4:00 pm KST
Event Details
Han-woong Yeom Academic Affiliation: CALDES, IBS & POSTECH Title: Nano-tsunami along atomic chains and domain walls for robust informatics Abstract: Storing and
Event Details
Han-woong Yeom
Academic Affiliation: CALDES, IBS & POSTECH
Title: Nano-tsunami along atomic chains and domain walls for robust informatics
Abstract:
Storing and manipulating information in robust and dissipationless ways is of prime interest in various fields of science and technology. Using topologically protected local excitations, form examples, skyrmions and Majorana fermions, such robust informatics may be realized. This talk reviews our own approach to this issue, which deals with new types of solitons in electronic systems. We will first discuss atomic chains formed on silicon surfaces in charge-density-wave ground states and their solitons. We recently identified individual electronic solitons in indium atomic chains on a Si(111) surface and, more recently, in silicon chains on stepped silicon surfaces . Due to their unique structures, they represent unprecedented topological systems of Z4 [1] and Z3 [2], respectively, with three and two distinct solitons. These solitons can store, deliver, and operate multi-level information bits, which are protected topologically [3]. We further demonstrate solitons with higher multiplicity can be formed as a form of mobile kinks [4] along the charge-density-wave domain walls on a 2D material of 1T-TaS2 [5]. Thus, the possibility of multi-level and topologically protected information processing with solitons, or solitonics, is well demonstrated. Further studies on soliton-defect, soliton-soliton, and soliton-excitation interactions are exciting for soliton applications.
References:
[1] S. M. Cheon, S. H. Lee, T. H. Kim, and H. W. Yeom, Science 350, 182 (2015).
[2] J. W. Park, E. Do, J. S. Shin, S. K. Song, O. P. Jelinek, and H. W. Yeom, Nature Nanotechnology 17, 244 (2022).
[3] S. M. Cheon, T. H. Kim, and H. W. Yeom, Nature Physics 13, 444 (2017).
[4] J. W. Lee, J. W. Park, and H. W. Yeom, PRL, under review (2022).
[5] D. Cho, G. Gye, J. Lee, S. H. Lee, L. Wnag, S-W. Cheong, and H. W. Yeom, Nature Commun. 8, 392 (2017)
Han Woong Yeom1,2
1Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang 37673, Korea.
2Department of Physics, POSTECH, Pohang 37673, Korea.
Time
(Tuesday) 3:00 pm - 4:00 pm
october 2022
Event Details
Jeremy Levy Affiliation: University of Pittsburgh Date: Oct 17th, 2022 (17:00 - 18:00, KST) Title: Correlated Nanoelectronics and the Second Quantum Revolution Abstract: Strongly correlated electronic materials and
Event Details
Jeremy Levy
Affiliation: University of Pittsburgh
Date: Oct 17th, 2022 (17:00 – 18:00, KST)
Title: Correlated Nanoelectronics and the Second Quantum Revolution
Abstract:
Strongly correlated electronic materials and quantum transport of nanoelectronic systems are areas of research that have traditionally followed non-intersecting paths. With the development of complex-oxide heterostructures and nanostructures, a nascent field of Correlated Nanoelectronics has emerged. My research program makes extensive use of nanoscale reconfigurability of a complex-oxide heterostructure formed from a thin layer of LaAlO3 grown on SrTiO3. Like an Etch-a-Sketch toy, the LaAlO3/SrTiO3 interface can be drawn (and erased) with 2 nm resolution to create a remarkable range of quantum devices. These nanoscale devices can be “aimed” back at the materials themselves to provide insight into their inner workings. This platform has already produced two novel phases of electronic matter: one in which electrons form bound pairs without becoming superconducting, and a family of one-dimensional degenerate quantum liquids formed from n-tuples of bound electrons. A rich and growing palette of quantum building blocks is currently being explored for applications in quantum computing, quantum simulation, and quantum sensing, major goals of the Second Quantum Revolution.
To participate in the talk, please, fill out the Registration Form →
Time
(Monday) 5:00 pm - 6:00 pm (KST)
Location
Center for Quantum Nanoscience
Research Cooperation Building,52 Ewhayeodae-gil, Daehyeon-dong
september 2022
Event Details
Harald Brune Academic Affiliation: Ecole Polytechnique Fédérale de Lausanne (EPFL) Title: The role of External Shells in the Magnetic Stability of Single
Event Details
Harald Brune
Academic Affiliation: Ecole Polytechnique Fédérale de Lausanne (EPFL)
Title: The role of External Shells in the Magnetic Stability of Single Rare-Earth Adatoms, new SAMs, and Graphene Transfer under UHV
Abstract:
An important and often neglected fact in the magnetic stability of single rare-earth adatoms is the spin-polarization of their outer shells. It stems from charge transfer to the surface [1] and gives rise to an additional magnetic moment that is strongly coupled to the large and well-screened moment of the 4f electrons [2]. We present experimental evidence for Dy/g/Ir(111) that the total angular momentum resulting from these coupled 4f 5d6s moments is in fact the good quantum number that decides which states are stable and which mechanisms for reversal exist in a given crystal field [3]. Recent theoretical works have pointed out the importance of valence 5d6s shells for single atom and single ion molecular magnets [4], however, direct experimental evidence for the importance of these shells in the spin dynamics was so far lacking.
We discuss the most recent single atom magnets (SAMs) with focus on two cases where the easy axis is lying in-plane. The first is Dy on the TiO2(100)-terminated Dy/SrTiO3(100) surface [5] and the second Dy on MgO bridge sites [6]. In the first case, we present XMCD results and in the second preliminary SP-STM results studying the two-state switching as function of tunnel bias that we discuss in the context of published XMCD data [7]. In order to cap, respectively, seal samples that are sensitive to oxidation and other chemical reactions in ambient, we have transferred graphene under ultra-high vacuum. Since this is potentially relevant also for single atom magnets, we present our results that show clean graphene transfer under UHV onto Cu(100) and Ir(111) target samples using a wafer bonding approach.
[1] M. Pivetta et al. PRB 98, 115417 (2018).
[2] M. Pivetta et al. PRX 10, 031054 (2020).
[3] A. Curcella et al. to be published (2022).
[4] V. Dubrovin et al. Chem. Communic. 55, 13963 (2019) & Inorg. Chem. Front. 8, 2373 (2021).
[5] V. Bellini et al. ACS Nano 16, 11182 (2021).
[6] C. Soulard et al. in preparation (2022).
[7] F. Donati et al. Nano Lett. 21, 8266 (2021).
[8] D. Merk et al. submitted (2022).
Time
(Thursday) 4:00 pm - 5:30 pm
august 2022
18aug4:00 pm5:00 pmJingcheng LiSun Yat-sen University4:00 pm - 5:00 pm KST
Event Details
Jingcheng Li Academic Affiliation: Sun Yat-sen University Title: Inducing magnetic properties in graphene nanostructures Abstract: Spin in carbon-based materials shows long coherence time, tunable
Event Details
Jingcheng Li
Academic Affiliation: Sun Yat-sen University
Title: Inducing magnetic properties in graphene nanostructures
Abstract:
Spin in carbon-based materials shows long coherence time, tunable coupling strength, and can be incorporated into scalable carbon platform, which makes it promising for quantum computing and spintronics applications. Predictions state that graphene structures with specific edge topology can spontaneously develop magnetism, but the difficulty in their synthesis and magnetism characterization hinders the experimental verification. Here in this talk, I will show you our latest results on the observation and manipulation of magnetic moments in such graphene open-shell nanostructures. The graphene open-shell nanostructures with different edge topology, size and doping are created on a gold surface through on-surface synthesis route with atomic precision. Using scanning tunneling spectroscopy, we can detect the presence of electron spins and map their localization. With the experimental results and theoretical simulations, I will demonstrate that how the electronic correlations, πbond frustration or topological band engineering can be used to induce spin states in graphene nanostructures.
Time
(Thursday) 4:00 pm - 5:00 pm
16aug2:30 pm3:30 pmYousoo KimUniversity of Tokyo2:30 pm - 3:30 pm KST
Event Details
Yousoo Kim Academic Affiliation: University of Tokyo Title: Single-molecule spectroscopy using localized-surface plasmon Abstract: Irradiation of light to the metallic nanostructure causes collective vibration
Event Details
Yousoo Kim
Academic Affiliation: University of Tokyo
Title: Single-molecule spectroscopy using localized-surface plasmon
Abstract:
Irradiation of light to the metallic nanostructure causes collective vibration of free electrons (plasmon), followed by the creation of an electromagnetic field, i.e., localized surface plasmon (LSP). The LSP has a characteristic interaction with matter, especially a single molecule. The scanning tunneling microscope (STM) is a versatile and powerful tool for investigating and controlling the chemistry of individual molecules on solid surfaces. We have developed an optical STM technology that combines the STM with light irradiation and detection technologies for our own purpose [1], which allows us to apply the LSP to exploring novel chemical reactions and spectroscopy based on the interaction between the LSP and electronic/vibrational quantum states of a single molecule at the STM junction. We have developed single molecule emission and absorption (Fig. 1(a)) spectroscopy [1] using the interaction between the LSP and a molecule, in which the LSP participates in the exciton formation in a target molecule [2,3]. Combining the emission and absorption spectroscopies, we visualized fluorescence resonance energy transfer between two different molecules [4]. We have also explored the detailed mechanism of single-molecule chemical dynamics induced by the LSP (Fig. 1(b)) [5]. We also applied the LSP to measure tip-enhanced resonance Raman spectra of a single molecule (Fig. 1(c)) [6]. Furthermore, we achieved an ultrahigh-energy resolution photoluminescence measurement of a single molecule using a tunable excitation laser (Fig. 1(d)) [7]. These optical setups enable a real-space measurement of photocurrent pathways at a single molecule (Fig. 1(e)) [8]. In this talk, I will discuss recent issues focusing on single-molecule spectroscopy based on the molecular excitation by localized surface plasmon at the STM junction, which has been applied to exploring the quantum states of a phthalocyanine and its derivatives.
REFERENCES
[1] H. Imada et al., Physical Review Letters, 119 (2017) 013901
[2] K. Miwa et al., Nano Letters, 19 (2019) 2803
[3] K. Kimura et al., Nature, 570 (2019) 210
[4] H. Imada et al., Nature, 538 (2016) 364
[5] E. Kazuma et al., Science, 360 (2018) 521
[6] R.B. Jaculbia et al., Nature Nanotechnology, 15 (2020) 105
[7] H. Imada et al., Science, 373 (2021) 95
[8] M. Imai-Imada et al., Nature 603 (2022) 829
Time
(Tuesday) 2:30 pm - 3:30 pm
16aug11:00 am12:00 pmYoungchan KimUniversity of Surrey11:00 am - 12:00 pm KST
Event Details
Youngchan Kim Academic Affiliation: University of Surrey Title: Quantum biology in fluorescent protein: a new model system to study quantum effects in biology Abstract: Quantum
Event Details
Youngchan Kim
Academic Affiliation: University of Surrey
Title: Quantum biology in fluorescent protein: a new model system to study quantum effects in biology
Abstract:
Quantum effects are usually thought to be too delicate to manifest in biology since random molecular interactions were thought to be instantaneously obliterated quantum coherent molecular interactions occurring in wet biological environments. However, recent biological, chemical, and physical breakthroughs have revealed that subtle quantum effects may shape biological processes and functions, as exemplified by photosynthesis, enzyme catalysed reactions, and magnetic field effects on spin-dependent reactions in biology, to name a few. Studying coherent dipole-dipole coupling between biomolecular systems is challenging but holds many fascinating, fundamental questions that will inspire new ways to better understand and enhance health and medicine. A recent study suggests that the yellow fluorescent proteins, VenusA206, exhibit room-temperature exciton coupling when they form a dimer. Because cryogenic temperature is not required to observe such quantum effects, genetically engineered fluorescent protein assemblies could inspire a new way towards developing biological quantum technologies, such as quantum-enhanced biosensors. In this talk, I will present the recent progress in studying quantum biology using fluorescent proteins.
Time
(Tuesday) 11:00 am - 12:00 pm
10aug10:30 am11:30 amJens WiebeUniversity of Hamburg, Germany10:30 am - 11:30 am KST
Event Details
Jens Wiebe Academic Affiliation: University of Hamburg Lecture: From Superconductivity to Topological Superconductivity This lecture is intended for Master and PhD students as
Event Details
Jens Wiebe
Academic Affiliation: University of Hamburg
Lecture: From Superconductivity to Topological Superconductivity
This lecture is intended for Master and PhD students as well as young Postdocs. After a short historical review of the discoveries of materials which are conventional and unconventional superconductors, I will give an introduction to Cooper pairing and the Bardeen–Cooper–Schrieffer (BCS) theory, the microscopic theory for the description of conventional superconductivity. Then, I will describe the quasiparticle excitation spectrum of such a superconductor and explain how it can be experimentally measured using scanning tunnel spectroscopy, both with normal-metal and superconducting tips. Subsequently, I will talk about the effects of magnetic fields and single magnetic impurities on a superconducting substrate, where the latter leads to the so-called Yu-ShibaRusinov bound states. Finally, I will explain different strategies to tailor a topological superconductor, including the spin chain platform where bands formed by the hybridization of Yu-Shiba-Rusinov states in chains of magnetic atoms in contact to a superconducting surface can host Majorana bound states.
Literature
C. Enss and S. Hunklinger, Low Temperature Physics (Springer 2005)
R. Gross and A. Marx, Festkörperphysik (De Gruyter 2014): unfortunately only in german so far…
Several original publications
Time
(Wednesday) 10:30 am - 11:30 am
08aug2:00 pm3:30 pmJens WiebeUniversity of Hamburg, Germany2:00 pm - 3:30 pm KST
Event Details
Jens Wiebe Academic Affiliation: University of Hamburg Title: Search for Large Topological Gaps and Isolated Majorana Bound States in Atom-by-Atom Fabricated Shiba Chains Abstract: Magnetic
Event Details
Jens Wiebe
Academic Affiliation: University of Hamburg
Title: Search for Large Topological Gaps and Isolated Majorana Bound States in Atom-by-Atom Fabricated Shiba Chains
Abstract:
Magnetic chains on s-wave superconductors evoke so-called Shiba bands inside the gap of the substrate. If these bands experience sufficiently strong spin-orbit coupling and overlap with the Fermi energy, a topologically nontrivial minigap can open up which protects zero energy Majorana bound states localized at the chains two ends. We study artificial spin chains, built atom-by-atom [1], with respect to such phenomena. By variation of substrate and adatom species and interatomic distances in the chain [2-5], we adjust the energies of the multi orbital YuShiba Rusinov states induced by the adatoms [2,3], their hybridizations [4], as well as the chains’ spin structures [5]. This enables us to tailor the multi-orbital Shiba bands formed by hybridizing Yu-Shiba Rusinov states such that topologically nontrivial minigaps open [6] and precursors of Majorana bound states appear [7]. Due to a narrow energetical width of these topological minigaps, the two components of the Majorana precursors from the two chain ends strongly hybridize, such that the desired protection by the topological minigap is not realized. In this talk, I will present our most recent experimental strategies in order to increase the width of the topological minigap [8-10] which will eventually lead to isolated and topologically protected Majorana bound states. I acknowledge funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) via the Cluster of Excellence ’Advanced Imaging of Matter’ (EXC 2056-project ID 390715994) and via the SFB-925- project 170620586.
[1] D.-J. Choi, N. Lorente, J. Wiebe, K. von Bergmann, A. F. Otte, A. J. Heinrich, Rev. Mod. Phys. 91, 041001 (2019).
[2] L. Schneider, M. Steinbrecher L. Rózsa, J. Bouaziz, K. Palotás, M. dos Santos Dias, S. Lounis, J. Wiebe, R. Wiesendanger, npj Quantum
Materials 4, 42 (2019).
[3] L. Schneider, S. Brinker, M. Steinbrecher, J. Hermenau, Th. Posske, M. dos Santos Dias, S. Lounis, R. Wiesendanger, J. Wiebe, Nature
Commun. 11, 4707 (2020).
[4] P. Beck, L. Schneider, L. Rózsa, K. Palotás, A. Lászlóffy, L. Szunyogh, J. Wiebe, R. Wiesendanger, Nature Commun. 12, 2040 (2021).
[5] L. Schneider, P. Beck, J. Wiebe, R. Wiesendanger, Science Advances 7, eabd7302 (2021).
[6] L. Schneider, P. Beck, T. Posske, D. Crawford, E. Mascot, S. Rachel, R. Wiesendanger, J. Wiebe, Nat. Phys. 17, 943 (2021).
[7] L. Schneider, P. Beck, J. Neuhaus-Steinmetz, T. Posske, J. Wiebe, R. Wiesendanger, Nature Nanotechnology 17, 384 (2022).
[8] P. Beck, L. Schneider, L. Bachmann, J. Wiebe, R. Wiesendanger, Phys. Rev. Materials 6, 024801 (2022).
[9] P. Beck, L. Schneider, R. Wiesendanger, J. Wiebe, arXiv:2205.10062 [cond-mat.supr-con] (2022).
[10] P. Beck, L. Schneider, R. Wiesendanger, J. Wiebe, arXiv:2205.10073 [cond-mat.supr-con] (2022.)
Time
(Monday) 2:00 pm - 3:30 pm
july 2022
Event Details
Paul Weiss Academic Affiliation: California NanoSystems Institute and Departments of Chemistry & Biochemistry, Bioengineering, and Materials Science & Engineering, UCLA, Los Angeles Title:
Event Details
Paul Weiss
Academic Affiliation: California NanoSystems Institute and Departments of Chemistry & Biochemistry, Bioengineering, and Materials Science & Engineering, UCLA, Los Angeles
Title: Atomically Precise Chemical, Physical, Electronic, and Spin Contacts and Interfaces
Abstract:
One of the key advances in nanoscience and nanotechnology has been our increasing ability to reach the limits of atomically precise structures. By having developed the “eyes” to see, to record spectra, and to measure function at the nanoscale, we have been able to fabricate structures with precision as well as to understand the important and intrinsic heterogeneity of function found in these assemblies. The physical, electronic, mechanical, and chemical connections that materials make to one another and to the outside world are critical. Just as the properties and applications of conventional semiconductor devices depend on these contacts, so do nanomaterials, many nanoscale measurements, and devices of the future. We discuss the important roles that these contacts can play in preserving key transport and other properties. Initial nanoscale connections and measurements guide the path to future opportunities and challenges ahead. Band alignment and minimally disruptive connections are both targets and can be characterized in both experiment and theory. I discuss our initial forays into this area in a number of materials systems.
Time
(Thursday) 11:00 am - 12:00 am
june 2022
29jun2:00 pm3:00 pmDaniel LossUniversity of Basel, Switzerland2:00 pm - 3:00 pm KST
Event Details
Daniel Loss Academic Affiliation: University of Basel Title: Hole spin qubits for quantum computing in Si and Ge quantum dots Abstract: Hole spin
Event Details
Daniel Loss
Academic Affiliation: University of Basel
Title: Hole spin qubits for quantum computing in Si and Ge quantum dots
Abstract:
Hole spin qubits are frontrunner platforms for scalable quantum computers in Si and Ge semiconductors because of their large spin-orbit interaction which enables ultrafast all-electric qubit control at low power. The fastest spin qubits to date are defined in long quantum dots with two tight confinement directions, when the driving field is aligned to the smooth direction [1]. However, in these systems the lifetime of the qubit is strongly limited by charge noise, a major issue in hole qubits. I will give an overview of recent theoretical and experimental results [1-5] that have led to a series of testable predictions such as sweet spots for devices in Si and Ge semiconductors currently implemented in the Swiss National Center on Spin Qubits led by the University of Basel and IBM Zurich.
References
[1] Ultrafast Hole Spin Qubit with Gate-Tunable Spin-Orbit Switch. F. N. M. Froning, L. C. Camenzind, O. A. H. van der Molen, A. Li, E. P. A. M. Bakkers, D. M. Zumbühl, F. R. Braakman; Nature Nanotechnology 16 (2021).
[2] Fully tunable hyperfine interactions of hole spin qubits in Si and Ge quantum dots.
S. Bosco and D.Loss, Phys. Rev. Lett. 127, 190501 (2021).
[3] Hole spin qubits in Si FinFETs with fully tunable spin-orbit coupling and sweet spots for charge noise. S. Bosco, B. Hetényi, and D.Loss; PRX Quantum 2, 010348 (2021).
[4] The germanium quantum information route. G. Scappucci, C. Kloeffel, F. A. Zwanenburg, D. Loss, M. Myronov, J.-J. Zhang, S. De Franceschi, G. Katsaros, and M. Veldhorst; Nat Rev Mater (2020).
[5] A hole spin qubit in a fin field-effect transistor above 4 Kelvin. L. C. Camenzind, S. Geyer, A. Fuhrer, R. J. Warburton, D. M. Zumbühl, A. V. Kuhlmann; Nature Electronics 2022.
Time
(Wednesday) 2:00 pm - 3:00 pm
29jun10:00 am11:00 amValeria SheinaUniversity Paris-Saclay, France10:00 am - 11:00 am KST
Event Details
Valeria Sheina Academic Affiliation: C2N, Université Paris - S aclay Talk title: The development of Quantum Technologies Abstract: Quantum spin states constitute
Event Details
Valeria Sheina
Academic Affiliation: C2N, Université Paris – S aclay
Talk title: The development of Quantum Technologies
Abstract:
Quantum spin states constitute a resource for the development of quantum technologies. They have been considered for the realization of quantum computers, quantum simulators and quantum sensors. These long-term goals demand for the identification of appropriate hosts for quantum spin states with long coherence time and compatible with microfabrication technologies. Because of their two-dimensional character that enables an easier localization of the dopants in the material, monoatomic layer of Van-der-Waals materials is of intense interest. My Ph.D. describes experimental works that address two issues in this field. First, the identification of point-defects with interesting spin properties in Van-der-Waals materials; second, the Electrical Detection of Magnetic Resonance (EDMR) in those Van-der-Waals materials.
My work addresses two layered materials possessing spin and valley degrees of freedom: the Br-doped 2H-MoTe2 semiconductor belonging to the transition metal dichalcogenide (TMD) family and graphene. In 2H-MoTe2, we found that the electronic levels of the Br-dopants electronic levels are hybridized to the valleys in the conduction band. This produces spin-valley states where the spin and valley quantum numbers are locked. Moreover, by spin resonance methods, we find that the Br dopant carries an unpaired spin with coherence lifetime reaching 50 ns at the lowest temperature of 4.2 K. This is of practical interest as such states can be manipulated conveniently by electric fields. In graphene, encapsulated in hBN. we show that the spin resonance can be detected by transport measurements and propose a simple model relating the spin-resonant signal to the time average of the perpendicular magnetization component <Mz>.
Time
(Wednesday) 10:00 am - 11:00 am
28jun3:30 pm4:30 pmMario RubenKIT Karlsruhe, Germany3:30 pm - 4:30 pm KST
Event Details
Mario Ruben Academic Affiliation: INT, IQMT, Karlsruhe Institute of Technology (KIT) & ISIS, CESQ, University of Strasbourg Talk title: Quantum Computing with
Event Details
Mario Ruben
Academic Affiliation: INT, IQMT, Karlsruhe Institute of Technology (KIT) & ISIS, CESQ, University of Strasbourg
Talk title: Quantum Computing with Molecules
Abstract:
Metal complexes will be proposed to acting as active quantum units for Quantum Computing (QC). We report on the implementation of metal complexes into nanometre-sized (single-)molecular spintronic devices by a combination of isotopologue chemistry, bottom-up self-assembly and top-down lithography techniques. The control of the Hilbert space of the molecular quantum magnets on conducting surfaces/electrodes will be shown and persistence of magnetic properties under confinement in Supramolecular Quantum Devices (SMQD) will be proven. The quantum behaviour (e.g.. superposition) of the metal complexes will be addressed at the single molecule level1-13 to finally implement a quantum algorithm on a TbPc2-Qudit performing quantum computing operations.10 Moreover, we will show that that the components of SMQDs as the Quantum Magnet14 and the graphene sheets15 can be made from CO2 guaranteeing a negative Carbon footprint and sustainability of the molecular approach towards QC.
References:
[1] S. Kyatskaya et. al. J. Am. Chem. Soc. 2009, 131, 15143-15151.
[2] M. Urdampilleta et al. Nature Mater. 2011, 10, 502-506.
[3] J. Schwöbel et. al. Nature Comms. 2012, 3, 953-956.
[4] R. Vincent et al. Nature 2012, 488, 357-360.
[5] M. Ganzhorn et al. Nature Nano. 2013, 8, 165–169.
[6] M. Ruben et. al. Nature Nano. 2013, 8, 377–389.
[7] S. Wagner et. al. Nature Nano. 2013, 8, 575–579.
[8] S. Thiele, et al. Science 2014, 344, 1135-1138.
[9] M. Ganzhorn, et. al. Nature Comms 2016, 7, 11443.
[10] C. Godfrin et al. PRL 2017, 119, 187702 (perspective article by A. Morello Nature Nano 2018, 13, 9-10).
[11] H. Biard et. al. Nature Comms 2021, 12, 4443.
[12] S. Kuppusamy et. al. Nature Comms 2021, 12, 2152.
[13] D. Serrano et al. Nature 2022, 603, 241.
[14] E. Pineda-Moreno et. al. Chem. Sci. 2017, 8, 1178-1185.
[15] C. Molin-Jiron et. al. ChemSusChem. 2019, 12, 3509 –3514.
Recent Reviews:
“Molecular Spin Qudits for Quantum Algorithms.”
- Moreno-Pineda, C. Godfrin, F. Balestro, W. Wernsdorfer, M. Ruben
Chem. Soc. Rev. 2018, 47, 501.
„Synthetic Engineering of the Hilbert Space of Molecular Qudits: Isotopoloque Chemistry.“
- Wernsdorfer, M. Ruben
Adv. Mat. 2019, 31, 1806687.
Time
(Tuesday) 3:30 pm - 4:30 pm
17jun11:00 am12:00 amFranz Josef GiessiblUniversity of Regensburg, Germany11:00 am - 12:00 am KST
Event Details
Franz Josef Giessibl Academic Affiliation: University of Regensburg Title: The character of chemical bonds to natural and artificial atoms revealed
Event Details
Franz Josef Giessibl
Academic Affiliation: University of Regensburg
Title: The character of chemical bonds to natural and artificial atoms revealed by atomic force microscopy
Abstract: Atomic force microscopy with CO terminated tips has demonstrated outstanding spatial resolution on organic molecules [1], metallic clusters [2] and many other samples. Experimental evidence and calculations show that the CO tip is chemically inert and probes organic molecules mainly by Paulirepulsion [3]. Thus, images of organic molecules, graphene, etc. observed with a CO tip can be interpreted as a map of the absolute charge density of the sample. The total charge density of a single adatom is approximately given by a Gaussian peak. While single silicon adatoms appear similar to a Gaussian peak when imaged by AFM with a CO terminated tip, copper and iron adatoms adsorbed on Cu(111) and Cu(110) appear as tori [2,4]. Experiments and DFT calculations show that the total charge density of Cu and Fe adatoms is approximately Gaussian–in contrast to a hypothesis that proposes 4spz hybridization of Cu and Fe adatoms on a Cu surface[4]. The bonding strength between the AFM tip and the atoms of the sample depends not only on the chemical identity but also on the coordination-corner atoms in clusters are more reactive than center atoms [5]. Progress in force resolution [6] opens up the fN-regime, enabling to study engineered surface structures such as quantum corrals [7] that can be viewed as artificial atoms. Surprisingly, these artificial atoms interact in a similar way with AFM tips as natural atoms, yet with a force of only 1/1000of what is experienced in natural atoms [8].
References:
[1] L. Gross et al.,Science325, 1110 (2009).
[2] M. Emmrich et al.,Science348, 308 (2015).
[3] N. Moll et al.,New Journal of Physics12, 125020 (2010).
[4] F. Huber et al.,Science366, 235 (2019).
[5] J. Berwanger et al.,Phys.Rev. Lett.124, 096001 (2020).
[6] A. Liebig et al.,New Journal of Physics22, 063040 (2020).
[7]M.F. Crommie, C.P. Lutz, D.M. Eigler,Science262, 218(1993).
[8] F. Stilp, et al.,Science372, 1196 (2021).
Date: June 17, 11:00 (KST)
Location: B1 Jupiter, Center for Quantum Nanoscience
Time
(Friday) 11:00 am - 12:00 am
may 2022
Event Details
Ali Yazdani Affiliation: Princeton University Date: May 31th, 2022 Title: Correlation, Topology, and Unconventional Superconductivity in a Moiré Material Video link: https://youtu.be/WeSo2IXsW0Q
Event Details
Ali Yazdani
Affiliation: Princeton University
Date: May 31th, 2022
Title: Correlation, Topology, and Unconventional Superconductivity in a Moiré Material
Video link: https://youtu.be/WeSo2IXsW0Q
Time
(Tuesday) 9:00 am - 10:00 am (KST)
Location
ZOOM Application
27may10:15 am11:15 amHosung SeoAjou University10:15 am - 11:15 am KST Jupiter Meeting Room
Event Details
Hosung Seo Academic Affiliation: Ajou University Date and Time of the Talk: May 27th, 2022; 10:15 - 11:15 First-principles theory of extending the spin
Event Details
Hosung Seo
Academic Affiliation: Ajou University
Date and Time of the Talk: May 27th, 2022; 10:15 – 11:15
First-principles theory of extending the spin qubit coherence time in hexagonal boron nitride
Negatively charged boron vacancies (VB–) in hexagonal boron nitride (h-BN) are a rapidly developing qubit platform in two-dimensional materials for solid-state quantum applications. However, their spin coherence time (T2) is very short, limited to a few microseconds owing to the inherently dense nuclear spin bath of the h-BN host. As the coherence time is one of the most fundamental properties of spin qubits, the short T2 time of VB– could significantly limit its potential as a promising spin qubit candidate. In this study, we theoretically proposed two materials engineering methods, which can substantially extend the T2 time of the VB– spin by four times more than its intrinsic T2. We performed quantum many-body computations by combining density functional theory and cluster correlation expansion and showed that replacing all the boron atoms in h-BN with the 10B isotope leads to the coherence enhancement of the VB– spin by a factor of three. In addition, the T2 time of the VB– can be enhanced by a factor of 1.3 by inducing a curvature around VB–. Herein, we elucidate that the curvature-induced inhomogeneous strain creates spatially varying quadrupole nuclear interactions, which effectively suppress the nuclear spin flip-flop dynamics in the bath. Importantly, we find that the combination of isotopic enrichment and strain engineering can maximize the VB– T2, yielding 207.2 and 161.9 μs for single- and multi-layer h-10BN, respectively. Furthermore, our results can be applied to any spin qubit in h-BN, strengthening their potential as material platforms to realize high-precision quantum sensors, quantum spin registers, and atomically thin quantum magnets.
[1] A. Gottscholl et al., Nat. Mater. 19, 540-545 (2020)
[2] A. Gottscholl et al., Sci. Adv. 7, eabf3630 (2021).
[3] M. Ye, H. Seo, and G. Galli, npj Comp. Mater. 5, 44 (2019).
Time
(Friday) 10:15 am - 11:15 am KST
february 2022
Event Details
David D. Awschalom Affiliation: University of Chicago Date: Feb 16th, 2022; 10:00 - 11:00 (KST) / Feb 15th, 19:00 - 20:00 (CT) Developing quantum systems with semiconductors and molecules Our technological preference for perfection
Event Details
David D. Awschalom
Affiliation: University of Chicago
Date: Feb 16th, 2022; 10:00 – 11:00 (KST) / Feb 15th, 19:00 – 20:00 (CT)
Developing quantum systems with semiconductors and molecules
Our technological preference for perfection can only lead us so far: as traditional transistor-
based electronics rapidly approach the atomic scale, small amounts of disorder begin to
have outsized negative effects. Surprisingly, one of the most promising pathways out of this
conundrum may emerge from current efforts to embrace defects to construct quantum
devices and machines that enable new information processing and sensing technologies
based on the quantum nature of electrons and atomic nuclei. Individual defects in diamond,
silicon carbide, and other wide-gap semiconductors have attracted interest as they possess
an electronic spin state that can be employed as a solid-state quantum bit at room
temperature. These systems have a built-in optical interface in the visible and telecom
bands, retain their coherence over millisecond timescales, and can be polarized,
manipulated, and read out using a simple combination of light and microwaves. We discuss
integrating single spin qubits into wafer-scale, commercial optoelectronic devices, extending
the coherence of these spin qubits, and demonstrating the control and entanglement of a
single nuclear spin with an electron spin.
Optically addressable spin qubits can also be created, engineered, and scaled through a
purely synthetic chemical approach. Moreover, these structures offer new opportunities to
construct hybrid systems. We demonstrate the optical initialization and readout, and
coherent control, of ground-state spins in organometallic molecules. This bottom-up
approach offers avenues to create designer qubits and to deploy the diverse capabilities of
chemical synthesis for scalable quantum technologies.
- This talk was not uploaded on the internet.
Time
(Wednesday) 10:00 am - 11:00 am (KST) / (Tuesday) Feb15th, 19:00 - 20:00 (CT)
Location
ZOOM Application
december 2021
Event Details
Danna Freedman Affiliation: F. G. Keyes Professor of Chemistry, Massachusetts Institute of Technology Date: Dec 16th, 2021; 10:00 - 11:00 (KST) / Dec 15th, 20:00 - 21:00 (EST) Chemically enabled atomistic design of
Event Details
Danna Freedman
Affiliation: F. G. Keyes Professor of Chemistry, Massachusetts Institute of Technology
Date: Dec 16th, 2021; 10:00 – 11:00 (KST) / Dec 15th, 20:00 – 21:00 (EST)
Chemically enabled atomistic design of quantum systems
Quantum information science encompasses all areas in which quantum
control can impact the world around us. Applications range from
quantum computing, to quantum sensing, to quantum communications.
Within each of these areas the requirements for a “good” quantum unit
differ. Chemistry offers a unique approach to quantum information
science, whereby we can harness the atomistic precision inherent in
synthetic chemistry to create structurally precise, reproducible, and
tunable units. Results in this area will be presented including
creating molecules that are analogues of NV centers which we dub
molecular color centers. These molecules feature optical read-out of
spin information and offer significant promise in the realm of sensing
and potentially communication.
- This talk was not uploaded on the internet.
Time
(Thursday) 10:00 am - 11:00 am (KST) / (Wednesday) Dec 15th, 21:00 - 22:00 (EST)
Location
ZOOM Application
november 2021
Event Details
Richard A. Layfield Academic Affiliation: Department of Chemistry, School of Life Sciences, University of Sussex, UK Date and Time of the Talk: Nov 17th, 2021; 17:00 - 18:00 (KST) Axial Crystal
Event Details
Richard A. Layfield
Academic Affiliation: Department of Chemistry, School of Life Sciences, University of Sussex, UK
Date and Time of the Talk: Nov 17th, 2021; 17:00 – 18:00 (KST)
Axial Crystal Fields and Single-Molecule Magnetism in Dysprosium Sandwich Compounds
Organometallic sandwich compounds play a leading role in the development of f-element chemistry. In addition to making significant contributions to our fundamental understanding of structure, bonding and reactivity in lanthanide and actinide compounds, organometallic sandwiches are used in catalysis and a variety of small-molecule activation processes.
The reactivity of f-element sandwich compounds often has no parallel with transition metals or main group elements and offers many opportunities for development. In contrast, the magnetic properties of f-element organometallics have not been studied extensively, which is surprising given the many applications of lanthanides in magnetic materials and related areas, such as MRI. This is particularly true in the case of single-molecule magnets (SMMs), a family of compounds that show magnet-like behaviour below a characteristic blocking temperature.
Since 2010, we have developed a large family of dysprosium SMMs based on the metallocene structural unit. We have applied our findings to develop a working model that allows the magnetic blocking temperature to be increased in a rational way. The culmination of our work is a dysprosium metallocene SMM with a blocking temperature of 80 K, which is (currently) the only example to function above liquid nitrogen temperatures.
Using our structure-property relationship, we are now focused on improving the SMM properties further. To do this, our attention has shifted toward a ligand that is well-known in transition metal chemistry but is extremely rare in the f-block: the strained ring species cyclobutadienyl (see image, above right). In this seminar I will present our recent findings in this area, showing how the beastly [4-C4(SiMe3)4]2– ligand can be tamed with appropriate control of the chemical conditions.
Link: https://youtu.be/eSERFVRZ7pw
Time
(Wednesday) 5:00 pm - 6:00 pm KST
Location
ZOOM Application
september 2021
Event Details
Nicolaj Betz Academic Affiliation: University of Stuttgart, Institute for Functional Matter and Quantum Technologies Date and Time of the Talk: Sept 14th, 2021;
Event Details
Nicolaj Betz
Academic Affiliation: University of Stuttgart, Institute for Functional Matter and Quantum Technologies
Date and Time of the Talk: Sept 14th, 2021; 17:00 – 19:00 (KST)
New insights into spin dynamics – Stochastic resonance as a tool
Stochastic scattering between magnetic atoms and electrons of a metal shortens excitation lifetimes and accelerates decoherence. However, this scattering also creates characteristic time scales, that carry information about dynamics of the system. Modulating the scattering close to a threshold leads to frequency-dependent synchronization of the spin of the magnetic atoms and the modulation [1]. This
effect, known as Stochastic Resonance, amplifies the dynamic response to the modulation and can be used to investigate quantum fluctuations of the system [2]. Here we introduce a measurement technique which uses the synchronization effect that underlies Stochastic Resonance to control and measure characteristic time scales of magnetic atoms with a scanning tunneling microscope. This enables the investigation of spin dynamics in a bandwidth ranging from milliseconds to picoseconds. In some spin structures this reveals multiple switching paths between higher excited states, thus providing insight into new, previously inaccessible dynamics.
[1] Hänze et al., Sci. Adv. 2021, 7 (2021).
[2] R. Löfstedt, S. N. Coppersmith, Phys Rev. Lett. 72, 1947 (1994)
Time
(Tuesday) 5:00 pm - 7:00 pm KST
Location
ZOOM Application
august 2021
Event Details
Arzhang Ardavan Affiliation: Professor of Physics at the Clarendon Laboratory, University of Oxford Date: August 17, 2021; Electric field control of spins in piezoelectrics, ferroelectrics, and molecules Magnetic fields are challenging to localise to
Event Details
Arzhang Ardavan
Affiliation: Professor of Physics at the Clarendon Laboratory, University of Oxford
Date: August 17, 2021;
Electric field control of spins in piezoelectrics, ferroelectrics, and molecules
Magnetic fields are challenging to localise to short length scales because their sources are electrical currents. Conversely, electric fields can be applied using electrostatic gates on scales limited only by lithography. This has important consequences for the design of spin-based information technologies: while the Zeeman interaction with a magnetic field provides a convenient tool for manipulating spins, it is difficult to achieve local control of individual spins on the length scale anticipated for useful quantum technologies. This motivates the study of electric field control of spin Hamiltonians [1].
Mn2+ defects in ZnO exhibit extremely long spin coherence times and a small axial zero-field splitting. Their environment is inversion-symmetry-broken, and the zero-field splitting shows a linear dependence on an externally applied electric field. This control over the spin Hamiltonian offers a route to controlling the phase of superpositions of spin states using d.c. electric field pulses, and to driving spin transitions using microwave electric fields [2]. An analogous sensitivity to external electric fields is exhibited by Fe3+ defect spins in the archetypal ferroelectric PbTiO3. The Fe spin anisotropy axis is set by the ferroelectric order, so the spin Hamiltonian is controllable by manipulating the ferroelectric polarization direction [3].
Electric fields may couple to spins in molecular magnets by a range of mechanisms [4], including via intramolecular exchange interactions or hyperfine interactions, as well as through anisotropy terms. Through chemical design it is possible to optimise the conditions for molecular spin-electric coupling, yielding systems showing strong effects [5].
References:
[1] W. Mims, The linear electric field effect in paramagnetic resonance (Oxford University Press, 1976)
[2] R.E. George et al., Phys. Rev. Lett. 110, 027601 (2013)
[3] J. Liu et al., Sci. Adv. 7, eabf8103 (2021)
[4] J. Liu et al., Phys. Rev. Lett. 122, 037202 (2019)
[5] J. Liu et al., arXiv:2005.01029, to appear in Nat. Phys.
- This talk was not uploaded on the internet.
Time
(Tuesday) 5:00 pm - 6:00 pm KST / 8:00 - 9:00 (GMT)
Location
ZOOM Application
july 2021
28jul4:00 pm5:00 pmRuslan TemirovForschungszentrum Jülich4:00 pm - 5:00 pm KST ZOOM Application
Event Details
Ruslan Temirov Academic Affiliation: Forschungszentrum Jülich Date and Time of the Talk: July 28th, 2021; 16:00 - 17:00 (KST) New mkSTM in Jülich: design,
Event Details
Ruslan Temirov
Academic Affiliation: Forschungszentrum Jülich
Date and Time of the Talk: July 28th, 2021; 16:00 – 17:00 (KST)
New mkSTM in Jülich: design, perfomance and first results
In my talk, I will introduce our new UHV STM operating at temperatures down to 26 millikelvin and high magnetic fields of up to 8 Tesla. The peculiarity of our setup is that it uses an adiabatic demagnetisation refrigerator (ADR) to reach its base temperature. Since this is the first instance of ADR use for STM, I will describe our microscope’s characteristics and modes of operation in some detail, after which I will demonstrate the first measurements we performed on superconducting Al(100) surface in the attempt to clarify the issue of our mkSTM junction’s effective electronic temperature.
Time
(Wednesday) 4:00 pm - 5:00 pm KST
Location
ZOOM Application
june 2021
Event Details
Junhee Choi Academic Affiliation: IQIM Postdoctoral Scholar, California Institute of Technology Date and Time of the Talk: June 18th, 2021; 13:30 - 14:30 Quantum
Event Details
Junhee Choi
Academic Affiliation: IQIM Postdoctoral Scholar, California Institute of Technology
Date and Time of the Talk: June 18th, 2021; 13:30 – 14:30
Quantum Metrology with Strongly Interacting Spin Systems
Quantum metrology is a powerful tool for explorations of fundamental physical phenomena and applications in material science and biochemical analysis. While in principle the sensitivity can be improved by increasing the density of sensing particles, in practice this improvement is severely hindered by interactions between them. Here, using a dense ensemble of interacting electronic spins in diamond, we demonstrate a novel approach to quantum metrology to surpass such limitations. It is based on a new method of robust quantum control, which allows us to simultaneously suppress the undesired effects associated with spin-spin interactions, disorder, and control imperfections, enabling a significant enhancement in coherence time compared to the state-of-the-art control sequences. Combined with optimal spin state initialization and readout directions, this allows us to achieve an ac magnetic field sensitivity well beyond the previous limit imposed by interactions, opening a new regime of high-sensitivity solid-state ensemble magnetometers.
Time
(Friday) 1:30 pm - 2:30 pm KST
Location
ZOOM Application
Event Details
Jinkyung Kim Date and Time of the Talk: June 1st, 2021; 14:00 - 15:00 Our 'Spin' invites you to our kick-off talk of the 'Spin Art' contest. We will introduce spin
Event Details
Jinkyung Kim
Date and Time of the Talk: June 1st, 2021; 14:00 – 15:00
Our ‘Spin’ invites you to our kick-off talk of the ‘Spin Art’ contest. We will introduce spin and quantum mechanics to the general public and in addition to that, there is a Q&A session. Jinkyung Kim who wrote the article about Spin and Magritte will tell you a nice story about that world. Don’t miss the talk!
Time
(Tuesday) 2:00 pm - 3:00 pm KST
Location
ZOOM Application
may 2021
Event Details
Andrea Morello Affiliation: University of New South Wales Date: May 25, 2021; 17:00 - 18:30 Quantum information and quantum foundations with spins in silicon Link: https://youtu.be/6L5qt3v_Eqw
Event Details
Andrea Morello
Affiliation: University of New South Wales
Date: May 25, 2021; 17:00 – 18:30
Quantum information and quantum foundations with spins in silicon
Time
(Tuesday) 5:00 pm - 6:30 pm KST
Location
ZOOM Application
Event Details
Danilo Longo Academic Affiliation: Synchrotron SOLEIL – L’orme des merisiers Saint-Aubin Date and Time of the Talk: May 20th, 2021; 15:30 - 16:30 In the maze of the interaction between magnetic
Event Details
Danilo Longo
Academic Affiliation: Synchrotron SOLEIL – L’orme des merisiers Saint-Aubin
Date and Time of the Talk: May 20th, 2021; 15:30 – 16:30
In the maze of the interaction between magnetic molecules and superconductivity
During the last decade, research on superconductivity found renewed interest since several theoretical works have announced the possibility to “fabricate” new topological phases by coupling superconducting solid-state systems with local magnetism and spin-orbit interaction [1]. Stabilization of such phases would be accompanied by the emergence of so-called Majorana edge states [2]. Experimental observation of such Majorana edge states would have a huge technological impact because they are considered good candidates for the realization of single qubits and their manipulation would provide a platform for the development of physical quantum computational systems.
To address this challenge, I focused on a hybrid system obtained by coupling self-assembled two-dimensional arrays of magnetic Metallo-organic molecules, i.e. manganese phthalocyanines (MnPcs), with thin films of lead (1 and 3 monolayers) grown on Si(111). In the first part of the talk, I will show the results [3] of the in-situ grown MnPcs/Pb/Si(111) system that has been characterized by Scanning TunnelingMicroscopy (STM) and spectroscopy (STS).
In the second part of the talk, I will focus on the results I obtained during the postdoc. One of the objectives of research in the field of organic spintronics is the understanding of the different paths through which localized spins in molecular lattices can interact to stabilize magnetic order, e.g. ferromagnetism or antiferromagnetism. In this regard, hybrid systems based on self-assembled layers of magnetic molecules, e.g.transition-metal phthalocyanines, supported by metallic substrates have been the subject of a huge number of studies [4,5]. When considering such organic/metal interface many types of coupling are at plays: in addition to direct exchange and superexchange coupling, so-called indirect exchange interactions that are mediated by the conduction electrons of the metallic substrate are also possible [6]. The interacting picture becomes dramatically more complicated if the substrate is allowed to be a superconductor. Magnetic atoms/molecules coupled to a superconductor induce bound states (Yu-Shiba-Rusinov(YSR) states [7]) within the superconducting gap. Under certain conditions, an overlap of YSR states associated to different magnetic atoms/molecules can mediate an indirect exchange interaction [8].
In order to explore and extract information about the magnetic signature of this mechanism, I carried out X-ray Magnetic circular dichroism (XMCD) experiments at 2K on different systems. In particular, I will present the results about (sub-) monolayers of MnPcs self-assembled on then on-superconducting HOPG and the superconducting 2H-NbSe2 [9].
References:
[1] Brauneckeret al., Phys. Rev. Lett. 111, 147202 (2013) / Hoffman S. et al., Phys. Rev. B92, 125422 (2015)
[2] SauJ.D. et al., Phys. Rev. B 82, 214509 (2010)
[3] D. Longo et al. J. Phys. Chem. C 36,19829 (2020)
[4] Wäckerlin C. et al., Chem. Commun. 51, 12958 (2015)
[5] Wu W. et al. , Phys. Rev. B 77, 184403 (2008)
[6] Wu W. et al. , Phys. Rev. B 77, 184403 (2008)
[7] Yu L., Acta Phys. Sin. 21, 75 (1965) / Shiba H., Prog. Theor. Phys. 40, 435 (1968) /Rusinov A.I., Sov. Phys. JETP Lett. 9, 85 (1969)
[8] Yao N.Y. et al. Phys. Rev. Lett. 113, 087202 (2014) / Hoffman S. etal., Phys. Rev. B 92, 125422 (2015) /Kezilebieke S. et al. Nano Lett. 2018, 18, 2311–2315 (2018)
[9] D.Longo et al., to be published
Time
(Thursday) 3:30 pm - 4:30 pm KST
Location
ZOOM Application
Event Details
Mingee Chung Academic Affiliation: School of Physics and Astronomy, the University of Birmingham, Birmingham, UK Date and Time of the Talk: May 14th,
Event Details
Mingee Chung
Academic Affiliation: School of Physics and Astronomy, the University of Birmingham, Birmingham, UK
Date and Time of the Talk: May 14th, 2021; 14:00 – 15:00
Quantum Spin liquids in One, Two, and Three Dimensions
Quantum spin liquids (QSLs) are exotic states of matter characterized by a long-range entanglement and fractionalization. DefyingLandau’s lesson on spontaneous symmetry breaking, the interacting spins in a QSL state do not develop any long-range order nor freezing down to absolute zero. During the last couple of decades, significant progress has been made in finding QSLs both in theory and materials realization of two-dimensional models.
However, there is yet a consensus whether the best-known candidates are truly QSLs as a smoking-gun experiment is lacking. On the other hand, the QSLis a rule than an exception in one dimension due to strong fluctuations and is well established. In this talk I will present some results of QSLs in one- and two-dimensional systems comparatively. It is also worth noting that an increasing number of candidates are found for three-dimensional QSL which will be discussed. It is my hope that I will be able to sketch some ideas to pursue together with QNS.
Time
(Friday) 2:00 pm - 3:00 pm KST
Location
ZOOM Application
april 2021
Event Details
Hans Boschker Affiliation: Max Planck Institute for Solid State Research, Germany Date: April 21, 2021; 17:00 - 18:00 Laser-Light for Epitaxy For the scientific development of quantum-matter heterostructures and
Event Details
Hans Boschker
Affiliation: Max Planck Institute for Solid State Research, Germany
Date: April 21, 2021; 17:00 – 18:00
Laser-Light for Epitaxy
For the scientific development of quantum-matter heterostructures and for a range of potential applications, the growth of high-purity heterostructures is required. We have developed a new thin-film deposition technique that is especially suited to the growth of an extremely wide range of heterostructures with atomic precision. Thermal laser epitaxy (TLE)uses chemical elements as sources that are evaporated with continuous-wave lasers [1]. The lasers’ virtually arbitrary power density allows for the evaporation of almost all elements of the periodic table in the same setup. This is demonstrated by showing elemental metal films of a large range of elements; from high-vapor-pressure elements like S and Bi to low-vapor-pressure elements like W and Ta [2]. I will discuss the benefits of thermal laser epitaxy for high-purity deposition of materials and heterostructures with almost all elements from the periodic table. Compared to existing methods such as molecular beam epitaxy and pulsed laser deposition, TLE is clean, simple, fast, and versatile. Furthermore, I will present the results of a new substrate heater that is based on a ~10 µm laser [3]. This laser light is directly absorbed by oxide crystals and therefore allows for a heating system that is ultra-clean, has very fast ramp rates, and can reach extremely high temperatures.
[1] Film Deposition by Thermal LaserEvaporation, W. Braun and J. Mannhart, AIP Advances 9, 085310 (2019).
[2] Thermal Laser Evaporation of elements from Across the Periodic Table, T.J. Smart, et al., J. Laser Appl. 33,022008 (2021).
[3] In situ Thermal Preparation of Oxide Surfaces, W. Braun, et al., Appl. Phys. Lett. Mater. 8, 071112 (2020).
Time
(Wednesday) 5:00 pm - 6:00 pm KST
Location
ZOOM Application
march 2021
Event Details
Lieven Vandersypen Affiliation: Delft University of Technology Date: March 23, 2021; 17:00 - 18:00 Quantum Computation and Simulation – Spins inside Excellent control of over 50 quantum bits has been achieved, but can we
Event Details
Lieven Vandersypen
Affiliation: Delft University of Technology
Date: March 23, 2021; 17:00 – 18:00
Quantum Computation and Simulation – Spins inside
Excellent control of over 50 quantum bits has been achieved, but can we scale up quantum computers to solve relevant problems? Quantum bits encoded in the spin state of individual electrons in silicon quantum dot arrays have emerged as a highly promising avenue. In this talk, I will present our vision of a large-scale spin-based quantum processor, and our ongoing work to realize this vision. I will also show how the same quantum dot arrays offer a powerful platform for analog quantum simulation of Fermi-Hubbard physics and quantum magnetism.
- This talk was not uploaded on the internet.
Time
(Tuesday) 5:00 pm - 6:00 pm KST
Location
ZOOM Application
Event Details
Iyyappa Rajan Paneer Affiliation: YST Research Fellow, Asia Pacific Center for Theoretical Physics (APCTP), POSTECH Campus, Korea. Date: March 16, 2021; 15:00 - 16:00 High-Temperature Thermoelectric Materials for Future Energy Conversion Applications
Event Details
Iyyappa Rajan Paneer
Affiliation: YST Research Fellow, Asia Pacific Center for Theoretical Physics (APCTP), POSTECH Campus, Korea.
Date: March 16, 2021; 15:00 – 16:00
High-Temperature Thermoelectric Materials for Future Energy Conversion Applications – A Combined First-principles and Boltzmann Transport Formalism approach
While most of the thermoelectric materials work well only at low and mid temperatures, high-temperature thermoelectric materials are equally important for future energy conversion applications. The applications include but not limited to the operation of deep spacecraft missions and the conversion of the waste heat from the nuclear reactors and high-temperature industrial reactors into electrical power generation. To accomplish this demand, I will talk about a few insights of designing high-temperature thermoelectric materials for energy conversion from my perspective. This presentation is based on the results obtained from the first-principles density functional theory (DFT) calculations and Boltzmann transport formalism along with an experimental literature validation wherever possible. In this talk, I will also elaborately discuss the transport properties such as Seebeck coefficient, electrical and thermal conductivities which are calculated using the various physical parameters of materials to obtain the optimum thermoelectric power-factor and figure-of-merit.
Time
(Tuesday) 3:00 pm - 4:00 pm KST
Location
ZOOM Application
february 2021
Event Details
Sander Otte Affiliation: Delft University of Technology, Netherlands Date: February 26, 2021; 16:00 - 17:00 Free coherent evolution of a coupled atomic spin system initialized by electron scattering Observing the free evolution of a
Event Details
Sander Otte
Affiliation: Delft University of Technology, Netherlands
Date: February 26, 2021; 16:00 – 17:00
Free coherent evolution of a coupled atomic spin system initialized by electron scattering
Observing the free evolution of a coupled spin system is an essential step towards studying collective quantum spin dynamics, as well as gaining insight into the fundamental mechanisms leading to spin excitation. Here, we combine pump-probe and ESR techniques with STM to study the free evolution of a single atomic spin depending on its level of entanglement with a second one. We build TiH dimers on MgO/Ag(100) in which the two spins are inherently detuned. We then make use of the magnetic interaction with the STM tip to tune the level of entanglement between the two spins: usingESR, we characterize the energy diagram of the dimer and identify the tip height at which both spin precess at the same frequency. Subsequently, we use a pump-probe scheme to, first, initialize the system via an electron induced spin excitation and, second, study the free evolution of the spin under the tip. We show that only when the two spins entangle, the excitation is swapped back and forth at a frequency that is given by their coupling strength. These results provide insight into the locality of electron-spin scattering: only the spin directly underneath the tip is affected, irrespective of its global quantum state.
Time
(Friday) 4:00 pm - 5:00 pm KST
Location
ZOOM Application
Event Details
Jose Reina Galvez Affiliation: CFM – Materials Physics Center Date: February 17, 2021; 17:00 - 18:00 Floquet theory applied to ESR Electron spin resonance (ESR) with the STM is a revolutionary technique that
Event Details
Jose Reina Galvez
Affiliation: CFM – Materials Physics Center
Date: February 17, 2021; 17:00 – 18:00
Floquet theory applied to ESR
Electron spin resonance (ESR) with the STM is a revolutionary technique that is permitting us to have unprecedented insight into quantum dynamical processes. To really achieve this goal, theory can be instrumental. To this end, we have developed a theory that computes the time-dependent electron current through a quantum system. The theory is based on the Floquet formalism that allows us to treat a complex time dependence, and it also uses non-equilibrium Green’s functions to deal with realistic bias drops in the quantum system. We can then easily identify the behavior of the electronic current with the actual quantum dynamics.
In this talk, I will first present the results of a spin-1/2 driven by a harmonic time-dependent bias. We will analyze the results of these calculations, showing the main ingredients of the theory. Then, we will move to two spins interacting via an exchange interaction and reproduce the experiments by Bae et al 2018. We evaluate the von Neumann entropy and show that entanglement is needed, but it is rather constant for all the cases evaluated here. Moreover, we show why the Rabi’s frequencies of the different transitions are changing, which gives us a handle on the actual parameters controlling the dynamics of this two-spin system. We will briefly show other results on spin-1 and spin-2 systems to show the versatility of our approach as well as its predictive power.
Time
(Wednesday) 5:00 pm - 6:00 pm KST
Location
ZOOM Application
january 2021
Event Details
Suyeon Cho Affiliation: Division of Chemical Engineering and Materials Science, Ewha Womans University Date: January 27, 2021; 15:00 - 16:00 Phase engineering in MoTe2 Two-dimensional atomic crystals such as transition metal dichalcogenides (TMDs) have
Event Details
Suyeon Cho
Affiliation: Division of Chemical Engineering and Materials Science, Ewha Womans University
Date: January 27, 2021; 15:00 – 16:00
Phase engineering in MoTe2
Two-dimensional atomic crystals such as transition metal dichalcogenides (TMDs) have recently attracted renewed interests for the important components of next-generation nanoelectronic devices. Most studies have focused on the semiconducting hexagonal 2H phases of TMDs. Other phases such as monoclinic 1T or 1T’ have not been studied well because it has been believed that those phases are thermodynamically unstable. However, two different phases, semiconducting hexagonal (2H) and metallic monoclinic (1T’), have been successfully synthesized as high quality single crystals in one of TMDs, MoTe2by the control of synthetic temperature. It is found that the electronic phase transition between semi-metallic (bulk) and semiconducting (few-layered) appears in newly found monoclinic 1T’-MoTe2. The phase engineering between semiconducting 2H and metallic 1T’ phase of MoTe2 can be achieved by laser-irradiation which produces Te vacancy on the surface of MoTe2. In-situ scanning transmission electron microscopy results combined with theoretical calculations reveal that the Te vacancy triggers the local phase transition in MoTe2. We performed the phase patterning on MoTe2 surface using the laser irradiation with 200 nm-sized spot. The insertion of a metallic 1T’- MoTe2 layer into the interface of an Au electrode and a semiconducting2H-MoTe2 film results a true 2D device, converting a schottky contact to an ohmic contact with large carrier mobility and a high on/off current ratio of 106.
Reference:
1. Suyeon Cho, S. Kim, J. H. Kim, J.Zhao, J. Seok, D. H. Keum, J. Baik, D.-H. Choe, K. J. Chang, K. Suenaga, S. W.Kim, Y. H. Lee, H. Yang, “PhasePatterning for Ohmic Homojunction Contact in MoTe2”, Science, 349(6248), 625 (2015)
2. D. H. Keum†, Suyeon Cho†, J. H. Kim, D.-H.Choe, H.-J. Sung, M. Kan, H. Kang, J.-Y. Hwang, S. W. Kim, H. Yang, K. J. Chang, Y. H. Lee, “Bandgapopening in few-layered monoclinic MoTe2”, Nature Physics, 11, 482-486 (2015)
Time
(Wednesday) 3:00 pm - 4:00 pm KST
Location
ZOOM Application
december 2020
09dec5:00 pm6:00 pmSebastian StepanowETH Zurich5:00 pm - 6:00 pm KST ZOOM Application
Event Details
Sebastian Stepanow Affiliation: ETH Zurich Date: December 9, 2020; 17:00 - 18:00 Single-atom electron paramagnetic resonance in a scanning tunneling microscope Scanning tunneling microscopy (STM) is a unique technique
Event Details
Sebastian Stepanow
Affiliation: ETH Zurich
Date: December 9, 2020; 17:00 – 18:00
Single-atom electron paramagnetic resonance in a scanning tunneling microscope
Scanning tunneling microscopy (STM) is a unique technique to achieve subatomic spatial resolution with simultaneous local spectroscopic information. The demonstration of spin sensitivity in STM experiments enabled the study of single magnetic atoms on a surface and their interactions. Despite these great advances, the energy resolution remains limited in tunneling-spectroscopy modes by the thermal energy broadening of the electronic tip and sample states (>1 meV at 4 K). This broadening limits the precise sensing of low-energy excitations, e.g., spin-flip excitations, which motivated efforts to reduce the STM operational temperature to the mK range and to apply large magnetic fields to obtain the required sensitivity.
Another promising way to overcome the thermally-limited energy resolution is to employ a resonance technique. In this regard, electron paramagnetic resonance (EPR) is an established method that has found diverse applications such as the identification of free radicals in chemical reactions, detection of spin-labeled molecules in biological systems, or the study of molecular nanomagnets.
Recently, the two techniques were combined to probe magnetic interactions and properties of single atoms on surfaces [1]. In this presentation, I will introduce the EPR-STM technique and highlight recent advances. Moreover, I will address the coupling of microwave driving fields into the STM junction [2] and discuss our current understanding of the underlying mechanism in EPR-STM [3].
[1] Baumann et al., Science 350, 417 (2015).
[2] Seifert et al., Physical Review Research 2, 013032 (2020).
[3] Seifert et al., Science Advances 6, eabc5511 (2020).
Time
(Wednesday) 5:00 pm - 6:00 pm KST
Location
ZOOM Application
november 2020
Event Details
Junho Suh Affiliation: Korea Research Institute of Standards and Science (KRISS) Date: November 24, 2020; 16:00 - 17:00 Nanomechanical oscillators for quantum technology Nanomechanical oscillators have been employed as
Event Details
Junho Suh
Affiliation: Korea Research Institute of Standards and Science (KRISS)
Date: November 24, 2020; 16:00 – 17:00
Nanomechanical oscillators for quantum technology
Nanomechanical oscillators have been employed as precision sensors in a diverse range of physical measurements. These tiny yet powerful mechanical sensors reached the single-phonon regime recently and they demonstrate operations near ground states repeatedly. I will review current progress in the field of quantum nanomechanical sensors and discuss KRISS’s approach in applying the nanomechanical oscillators for quantum technology.
- This talk was not uploaded on the internet.
Time
(Tuesday) 4:00 pm - 5:00 pm KST
Location
ZOOM Application
Event Details
Dinh Loc Duong Affiliation: Center for Integrated Nanostructure Physics, IBS, Korea Date: November 19, 2020; 16:00 - 17:00 The seminar will be held online, if you
Event Details
Dinh Loc Duong
Affiliation: Center for Integrated Nanostructure Physics, IBS, Korea
Date: November 19, 2020; 16:00 – 17:00
The seminar will be held online, if you want to join the meeting, please, write to us at info@qns.science.
Diluted Magnetic Semiconductors in Flatland and Beyond
In the first part of this talk, the evidence of the long-range magnetic order in V-doped WSe2 semiconductors will be presented. The magnetic domains of the long-range ferromagnetic order are observed by magnetic force microscopy at room temperature. More importantly, the magnetic domains can be modulated by a gate bias, which is concrete evidence for the ferromagnetic semiconducting characteristics. The mechanism behind the formation of the long-range order will be also discussed and investigated through scanning tunneling spectroscopy and density functional theory.
In the second part, the giant Zeeman shift from the spin-polarized state in WSe2doped with a small amount of vanadium atoms (~0.15%) by investigating resonant magneto tunneling spectroscopy of a vertical graphite/V-WSe2/graphiteheterojunction will be discussed. The p-type character of the doping state is located near the valence band, substantially shifted under an external magnetic field at 7.8 meV/T with a giant g factor of approximately 135, an order of magnitude higher than that of other 2D magnetic semiconductors. The evidence of the spin-polarized band edges of V-doped WSe2 is also confirmed by circular-polarized photoluminescence.
In the last part, some preliminary observations of possible spin-frustration as well as topological characteristics in V-doped WSe2 will be presented.
Time
(Thursday) 4:00 pm - 5:00 pm KST
Location
ZOOM Application
Event Details
Scanning Probe Microscopy: Current Status and Future Trends The virtual symposium “Scanning Probe Microscopy: Current Status and Future Trends” will be held online jointly by the IBS Center for Quantum Nanoscience
Event Details
Scanning Probe Microscopy: Current Status and Future Trends
The virtual symposium “Scanning Probe Microscopy: Current Status and Future Trends” will be held online jointly by the IBS Center for Quantum Nanoscience (QNS) at Ewha Womans University and School of Physics of Peking University on Nov. 9-10, 2020.
It aims at bringing together the academic and industrial researchers of the SPM community to present and discuss their latest results, exchange ideas, and inspire new thoughts. It is planned to address both fundamental and application aspects of SPM, with special emphasis on the emergent techniques that will lead the future trends of SPM.
We hope that the symposium will help to inspire a broad vision for the future of SPM-related techniques and fields. In particular, the event should provide an avenue for stimulating discussions, to identify new opportunities, and promote collaborations.
Time
9 (Monday) 5:00 pm - 10 (Tuesday) 11:00 pm KST
Location
ZOOM App.
Event Details
Lukas Spree Affiliation: Leibniz Institute for Solid State and Materials Research, Dresden, Germany Date: November 4, 2020; 16:00 - 17:00 The seminar will be held online,
Event Details
Lukas Spree
Affiliation: Leibniz Institute for Solid State and Materials Research, Dresden, Germany
Date: November 4, 2020; 16:00 – 17:00
The seminar will be held online, if you want to join the meeting, please, write to us at info@qns.science.
Abstract:
Lanthanide Dimetal fullerenes of the composition Ln2@C80 (Ln=Gd…Er, Y) feature a single electron bond between their metal atoms, which leads to exceptionally stable single molecule magnets. This, however, also makes the isolation of these compounds challenging, because of an unpaired electron located on the fullerene cage, which leads to immediate precipitation in the nonpolar solvents tradi-tionally used in their chromatographic separation. Benzylation of the cage has been shown to stabilize the dimetal fullerenes in nonpolar solvents, leaving the single electron bond, and thus the magnetic properties, intact. Optimization of the isolation procedure to obtain various isomerically pure com-pounds of the composition (Ln1-Ln2)@C80-CH2Ph comprises one part of this work. Additionally, chemical functionalization of the cage with a pyrene labeled linker and the formation of fullerene self-assembled monolayers on graphene and similar surfaces was undertaken. It is shown that the deposi-tion does not impact the magnetic properties of the molecules in a negative way.
Time
(Wednesday) 4:00 pm - 5:00 pm KST
Location
ZOOM Application
october 2020
Event Details
Je-Geun Park Affiliation: Department of Physics and Astronomy, Seoul National University Date: October 7, 2020; 14:30 - 16:30 The seminar will be held online, if you
Event Details
Je-Geun Park
Affiliation: Department of Physics and Astronomy, Seoul National University
Date: October 7, 2020; 14:30 – 16:30
The seminar will be held online, if you want to join the meeting, please, write to us at info@qns.science.
Current status and perspectiveof magnetic van der Waals materials research
The discovery of graphene in 2004 took the scientific community by surprise and virtually transformed the research landscape by creating a then-new field of 2dmaterials. However, despite the unique properties of many van der Waals materials since discovered, it has certain limitations in terms of exploring novel and new physical properties. Magnetism is a case in point. Until a couple of groups and I started to work on the much-neglected magnetic van der Waals materials, virtually nothing was known about it. However, with a series of publications, including those from my group, this field of magnetic van der Waals materials has become a fast emerging field in materials science. In this presentation, I would like to take you through the intellectual journey I made since 2010 and eventually discovering a novel quantum spin-entangled exciton NiPS3more recently. I will end my talk by giving a personal view of prospects for future research.
References:
[1] Je-Geun Park, J.Phys. Condens. Matter 28, 301001 (2016)
[2] Cheng-Tai Kuo, et al., Scientific Reports 6, 20904 (2016)
[3] Jae-Ung Lee, et al., Nano Lett. 16, 7433 (2016)
[4] So Yeun Kim, et al., Phys. Rev. Lett. 120, 136402 (2018)
[5] K. S. Burch, D.Mandrus, and Je-Geun Park, Nature 563, 47 (2018)
[6] Kangwon Kim, et al., Nature Comm. 10, 345 (2019)
[7] H Chu, et al., Phys. Rev. Lett. 124, 027601 (2020)
[8] S. Kang, et al., Nature 583, 785 (2020)
Time
(Wednesday) 2:30 pm - 4:30 pm KST
Location
ZOOM Application
september 2020
Event Details
André-Jean Attias Affiliation: CNRS / SorbonneUniversité / Yonsei University Date: September 17, 2020; 15:00 - 16:00 The seminar will be held online, if you want to join the meeting, please, write to us
Event Details
André-Jean Attias
Affiliation: CNRS / SorbonneUniversité / Yonsei University
Date: September 17, 2020; 15:00 – 16:00
The seminar will be held online, if you want to join the meeting, please, write to us at info@qns.science.
Electronic Decoupling Strategies for Emitting Graphene-BasedHybrid Platforms: Surface-Confined Supramolecular Self-Assembly as Tool
TElectronicdecoupling of molecular chromophores from graphene to preserve their electronic and optical properties with the objective to elaborate light-responsive hybrid systems for new electronic and optoelectronic nanodevices remains largely unexplored.
In this context, the supramolecular self-assembly of organic building blocks on graphene is an original bottom-up approach towards novel materials displaying unusual properties.[1] Hence, the possible fine-tuning of inter-constituents distances and orientations offered by the design of the building blocks makes the self-assembly approach very appealing for adjusting graphene photonic properties.
Here, we present two examples of electronic decoupling strategies we have recently developed.
In the first one, the quenching of the fluorescence of the adsorbed dye by the adjacent graphene is hindered at the molecular scale. In this spacer-based approach, a specifically designed dual-functionalized building block was self-assembled on graphene leading to the first light-emitting graphene-based hybrid 2D system [2].
The second example is based on surface-confined host-guest chemistry used to trap afunctional 3D building blocks into a large 2D nanoporous template on graphene [3]. This noncovalent graphene functionalization approach allows the immobilization, in a well-defined 2D nanoporous network, of an afunctional 3D complex that projects a dye-based ligand away from the surface and aligned along the normal direction. Thanks to this strategy of decoupling from the graphene as well as the orientation and intermolecular distance control, the platform emits light with the same characteristics as in dilute solution [4].
This decoupling method could open perspectives in the field of electrically induced luminescence at the single-molecule level through STM tip-induced electrical fields.
[1] L. Sosa-Vargas, E. Kim, A. J.Attias, Materials. Horizons, 4, 570(2017)
[2] S. LeLiepvre, P. Du, D. Kreher, F. Mathevet, A. J. Attias, C. Fiorini-Debuisschert,L. Douillard, F. Charra, ACS Photonics,3, 2291−2296 (2016)
[3] R. Brisse, D. Guianvarc’h, C. Mansuy, S. Sagan, D. Kreher, L. Sosa-Vargas, L. Hamitouche,V. Humblot, I. Arfaoui, V. Labet, C. Paris, C. Petit, A. J. Attias, Chem. Commun., 54, 10068 (2018)
[4] B. Kim, E.Kim, I. Arfaoui, C. Paris, C. Petit, A. J. Attias, Materials Horizons, DOI:10.1039/D0MH00950D (2020)
Time
(Thursday) 3:00 pm - 4:00 pm KST
Location
ZOOM Application
august 2020
Event Details
Je-Geun Park Affiliation: Department of Physics and Astronomy, Seoul National University Date: August 19, 2020; 16:00 - 17:00 Location: Saturn Seminar Room Current status and perspective of magnetic van der Waals materials research The discovery
Event Details
Je-Geun Park
Affiliation: Department of Physics and Astronomy, Seoul National University
Date: August 19, 2020; 16:00 – 17:00
Location: Saturn Seminar Room
Current status and perspective of magnetic van der Waals materials research
The discovery of graphene in 2004 took the scientific community by surprise and virtually transformed the research landscape by creating a then-new field of 2d materials. However, despite the unique properties of many van der Waals materials since discovered, it has certain limitations in terms of exploring novel and new physical properties. Magnetism is a case in point. Until a couple of groups and I started to work on the much-neglected magnetic van der Waals materials, virtually nothing was known about it. However, with a series of publications, including those from my group, this field of magnetic van der Waals materials has become a fast emerging field in materials science. In this presentation, I would like to take you through the intellectual journey I made since 2010 and eventually discovering a novel quantum spin-entangled exciton NiPS3 more recently. I will end my talk by giving a personal view of the prospect for future research.
[1] Je-Geun Park, J.Phys. Condens. Matter 28, 301001 (2016)
[2] Cheng-Tai Kuo, et al., Scientific Reports 6, 20904 (2016)
[3] Jae-Ung Lee, et al., Nano Lett. 16, 7433 (2016)
[4] So Yeun Kim, et al., Phys. Rev. Lett. 120, 136402 (2018)
[5] K. S. Burch, D.Mandrus, and Je-Geun Park, Nature 563, 47 (2018)
[6] Kangwon Kim, et al., Nature Comm. 10, 345 (2019)
[7] H Chu, et al., Phys. Rev. Lett. 124, 027601 (2020)
[8] S. Kang, et al., Nature 583, 785 (2020)
Time
(Wednesday) 4:00 pm - 5:00 pm KST
june 2020
Event Details
Virtual Workshop on Scanning Probe Microscopy Date: June 18, 2020 Time: 9:00 - 13:00 CEST (16:00 - 20:00 KST) Location: ZOOM Virtual SPM is a free online workshop on recent advances in
Event Details
Virtual Workshop on Scanning Probe Microscopy
Date: June 18, 2020
Time: 9:00 – 13:00 CEST (16:00 – 20:00 KST)
Location: ZOOM
Virtual SPM is a free online workshop on recent advances in scanning probe techniques, in particular low-temperature UHV scanning tunneling microscopy and atomic force microscopy.
With three invited talks, discussion time and a live poster session to provide further opportunity to share ideas and results, we hope this event will bring the community together to discuss the latest advances and keep sharing results despite the current lack of in-person conferences. Registration is open!
This workshop is organized with the support of the Virtual Science Forum, a platform that helps with the organization of online conferences.
Time
(Thursday) 4:00 pm - 8:00 pm KST
Location
ZOOM Application
Event Details
Andreas Heinrich Date: June 15, 2020 Time: 17:00 -18:00 The Talk is provided by orginizers from Aalto University, Finland Click here to register >> Virtual Talk - Electron Spin Resonance of single atoms on
Event Details
Andreas Heinrich
Date: June 15, 2020
Time: 17:00 -18:00
The Talk is provided by orginizers from Aalto University, Finland
Virtual Talk – Electron Spin Resonance of single atoms on a surface observed with STM
Scanning Tunneling Microscopy (STM) can be combined with electron spin resonance [1]. The major advantage of spin resonance is the fact that the energy resolution is independent of the temperature and thus can be much higher than a Fermi-function limited spectroscopy technique such as STM tunneling. In ESR STM we apply a microwave-frequency electric field to the STM tunnel junction and convert this AC electric field into a driving field for the ESR [2]. We find an energy resolution in ESR STM, which is about 10,000 times better than low-temperature STM.
Here we will focus on two examples: Fe and Ti atoms on MgO on Ag(100). Fe on MgO has a spin of S=2 with a strong out-of-plane easy-axis magnetic anisotropy. ESR active Fe atoms can be used to measure the local magnetic field very precisely and with atomic-scale spatial resolution. We will use this to measure the magnetic field emanating from a stable single-atom magnet nearby: Ho on MgO [3].
Ti atoms on MgO are an S=1/2 electron system (when a single Hydrogen is attached) with an interesting nuclear spin system, consisting of several isotopes (I=0, I=5/2 and I=7/2). ESR STM can measure the hyperfine interaction of the electron spin with the nuclear spin of the Ti atom [4]. The hyperfine interaction is a sensitive measure of the local bonding geometry.
ESR STM is just in its infancy with many groups joining this research effort.
Support from Institute for Basic Science (IBS-R027-D1) is gratefully acknowledged.
References:
[1] Susanne Baumann, William Paul, Taeyoung Choi, Christopher P. Lutz, Arzhang Ardavan, Andreas J. Heinrich, “Electron Paramagnetic Resonance of Individual Atoms on a Surface”, Science 350, 417 (2015)
[2] Reina Gálvez, C. Wolf, F. Delgado, and N. Lorente, Physical Review B 100, 035411 (2019)
[3] Fabio Donati, S Rusponi, Sebastian Stepanow, C Wäckerlin, Aparajita Singha, Luca Persichetti, R Baltic, K Diller, Francois Patthey, E Fernandes, Jan Dreiser, Željko Šljivančanin, K Kummer, Corneliu Nistor, Pietro Gambardella, Harald Brune, Science 352, 318 (2016)
[4] Philip Willke, Yujeong Bae, Kai Yang, Jose L. Lado, Alejandro Ferrón, Taeyoung Choi, Arzhang Ardavan, Joaquín Fernández-Rossier, Andreas J. Heinrich and Christopher P. Lutz, “Hyperfine interaction of individual atoms on a surface”, Science 362, 336 (2018)
Time
(Monday) 5:00 pm - 6:00 pm KST
Location
ZOOM Application
Event Details
Event Details
Affiliation: Ulsan University, South Korea
Date: June 15, 2020
Time: 15:00 -16:00
Emerging Spin-Related Phenomena in the Non-Centrosymmetric Artificial Superlattice
Various spin-relatedphenomena, such as chiral texture formation, spin-orbit torque, andRashba-induced magnetic anisotropy, have been important issues in spintronicsfield. Those phenomena are known to be observable in a bilayer structurecomposed of a ferromagnet and a heavy metal thin films with strong spin-orbitcoupling. In addition, relevant orbital hybridization is also crucial factor.Therefore, researches are limited with few material cases, which has strongspin-orbit coupling, large Berry curvature in a band, and good spintransparency. In this talk, I will introduce a new concept of a materialsystem, namely, a non-centrosymmetric artificial superlattice. I will presentthat several artificial superlattices that show large spinorbit torque, and Dzyaloshinksii-Moriya interaction. Non-centrosymmetricartificial superlattices will be a new class of material design for spinorbitronic devices.
Time
(Monday) 3:00 pm - 4:00 pm KST
may 2020
Event Details
Wonjun Jang - Farewell Symposium The symposium will be provided just for QNS Members and Visitors! Date: May 28, 2020 Time: 16:00 -17:00 Location: Saturn Seminar Room (QNS, 3F, 367)
Event Details
Wonjun Jang – Farewell Symposium
The symposium will be provided just for QNS Members and Visitors!
Date: May 28, 2020
Time: 16:00 -17:00
Location: Saturn Seminar Room (QNS, 3F, 367)
Time
(Thursday) 4:00 pm - 5:00 pm KST
april 2020
20aprallday23Event CancelledESR-STM WorkshopINL, Portugal(All Day)
Event Details
ESR-STM Workshop Due to COVID-19 the organizers have postponed the workshop. Updates to come! Visit Dates: April 20-23, 2020 Location: International Iberian Nanotechnology Laboratory, Portugal The discovery of Scanning Tunneling Microscope
Event Details
ESR-STM Workshop
Due to COVID-19 the organizers have postponed the workshop. Updates to come!
Visit Dates: April 20-23, 2020
Location: International Iberian Nanotechnology Laboratory, Portugal
The discovery of Scanning Tunneling Microscope (STM) Electron Spin Resonance (ESR) is opening new venues in surface quantum nanoscience. This workshop will bring together experts in this emerging area to present latest developments and discuss future work.
Participation only by invitation
Time
april 20 (Monday) - 23 (Thursday)
Event Details
Tobias Bilgeri ________________________________________________________________________________ The Talk is postponed. The new day and time will be updated soon ________________________________________________________________________________ Academic Affiliation: Center for Quantum Nanoscience Date: will be updated soon Time: will be updated soon ESR-STM studies of
Event Details
Tobias Bilgeri
________________________________________________________________________________
The Talk is postponed. The new day and time will be updated soon
________________________________________________________________________________
Academic Affiliation: Center for Quantum Nanoscience
Date: will be updated soon
Time: will be updated soon
ESR-STM studies of Dy and FePc on MgO
In 2016 it was discovered that individual Ho atoms on MgO can show magnetic bistability with record breaking temporal, thermal and magnetic field stability. During our first research project as part of my stay at QNS, we discovered that Dy atoms in many ways exceed the stability of Ho. We find anisotropy barriers roughly twice as large as in Ho, as well as superior robustness against low field demagnetization processes as inferred from a novel ESR-STM technique. We believe that this is a result of a similar physical environment as found for Ho but with additional symmetry protection due to a non-integer spin ground state in the 4f9 configuration of Dy. Furthermore we demonstrate facile atomic manipulation, which allows to engineer precise local magnetic fields with sub-nanometer precision.
During our second research project, we demonstrate for the first time electron spin resonance measurements of individually addressable molecular spins on a surface. Using the spin-1/2 system FePc, we carry out ESR measurements in a vector field and find an isotropic moment of 0.97muB. We coherently manipulate the spin and find coherence times of 42 ns in Rabi experiments. Using a Hahn echo scheme, we show that the intrinsic coherence time is 180 ns with tunneling electrons presenting the dominant source of decoherence. Finally we demonstrate that FePc molecules self-assemble in a commensurate lattice while at the same time retaining the spin properties of individual molecules. We spatially resolve the molecular interactions using local magnetic resonance imaging and demonstrate that the phase coherence time is fully preserved in molecules within a lattice.
Time
(Thursday) 4:00 pm - 5:00 pm KST
Event Details
Tobias Bilgeri ________________________________________________________________________________ The Talk is postponed. The new day and time will be updated soon ________________________________________________________________________________ Academic Affiliation: Center for Quantum Nanoscience Date: April 9, 2020 Time: 16:00 - 17:00 Upgrade of a scanning tunneling
Event Details
Tobias Bilgeri
________________________________________________________________________________
The Talk is postponed. The new day and time will be updated soon
________________________________________________________________________________
Academic Affiliation: Center for Quantum Nanoscience
Date: April 9, 2020
Time: 16:00 – 17:00
Upgrade of a scanning tunneling microscope for spin resonance
The addition of electron spin resonance to the STM-toolbox greatly increased the physical phenomena accessible in STM experiments. For this reason we upgraded throughout 2017-2018 a homebuilt, low temperature, high magnetic field STM to become world’s second ESR-STM. I will give a general introduction into ESR-STM and describe in detail the technical steps needed for the upgrade.
Time
(Thursday) 4:00 pm - 5:00 pm KST
february 2020
Event Details
Hervé Aubin Academic Affiliation: C2N, Department of Nanoelectronics, CNRS, France Research Area: STM spectroscopy, Superconductivity, Topological Insulators Research stay period: February 2020 - July 2020 Talk: February 25th, 16:00 – 17:00; Saturn Seminar
Event Details
Hervé Aubin
Academic Affiliation: C2N, Department of Nanoelectronics, CNRS, France
Research Area: STM spectroscopy, Superconductivity, Topological Insulators
Research stay period: February 2020 – July 2020
Talk: February 25th, 16:00 – 17:00; Saturn Seminar room (3F-367)
Anomalous Phase Shift and Spectral Signature of Equal Spin Triplet
A description of the talk will be updated soon!
Time
(Tuesday) 4:00 pm - 5:00 pm
Event Details
Delegation from Forschungszentrum Jülich Academic Affiliation: Quantum Nanoscience Division, Peter Grünberg Institut, Forschungszentrum Jülich Visit Dates: February 24-28, 2020
Event Details
Delegation from Forschungszentrum Jülich
Academic Affiliation: Quantum Nanoscience Division, Peter Grünberg Institut, Forschungszentrum Jülich
Visit Dates: February 24-28, 2020
Time
february 24 (Monday) - 28 (Friday)
Event Details
Markus Ternes Academic Affiliation: Quantum Nanoscience Division, Peter Grünberg Institut, Forschungszentrum Jülich Research Area: Understing fundamental properties on the nanoscale with the focus on magnetic excitations and correlated systems. Talk: February 21,
Event Details
Markus Ternes
Academic Affiliation: Quantum Nanoscience Division, Peter Grünberg Institut, Forschungszentrum Jülich
Research Area: Understing fundamental properties on the nanoscale with the focus on magnetic excitations and correlated systems.
Talk: February 21, 2020
Fitting Model for Spin Excitation
In this introductory lecture Prof. Markus Ternes will outline the fundamental considerations necessary to calculate the current transport through magnetic structures in a scanning tunneling setup using well established perturbation models. He will discuss the influence of higher order scattering on the spectrum and the limitations of the perturbative approach in this respect. Using the below provided scripts Prof.Ternes will discuss how one can use the ‘Graphical User Interface’ to simulate and fit single and complex spin structures in the “zero-current” and dynamical limit.
Participants interested in this lecture should bring their own laptop with them to directly use the scripts. For this, please install beforehand Scilab_6.0.2 (available without charge for Windows, Mac, and Linux from https://www.scilab.org/).
Time
(Friday) 1:30 pm - 2:30 pm
13feb4:00 pm5:00 pmAli YazdaniPrinceton University, USA4:00 pm - 5:00 pm Saturn Seminar Room
Event Details
Ali Yazdani Academic Affiliation: Princeton University, USA Research Area: At the forefront of quantum materials research is the goal to understand how new quantum phenomena can emerge from the topology of
Event Details
Ali Yazdani
Academic Affiliation: Princeton University, USA
Research Area: At the forefront of quantum materials research is the goal to understand how new quantum phenomena can emerge from the topology of electronic wavefunctions or correlations arising from electron-electron interactions. The Yazdani Lab has contributed significantly to this research paradigm by harnessing the power of high-resolution scanning tunneling microscopy (STM) techniques to directly visualize electronic wavefunctions in topological and correlated quantum materials.
Talk: February 13, 2020, 16:00-17:00
Majorana in Chains and Hinges
In recent years, following pioneeringtheoretical work of Kitaev and others, we have learned how to engineermaterials that harbor quasiparticles that behave similar to fermions thatMajorana had first envisioned. In particular, there has been a focus onone-dimensional topological superconductor that harbor Majorana zero modes(MZM) that can potentially be used to make fault-tolerant topological quantumcomputation possible. We have proposed and implemented a platform forrealization of topological superconductivity and MZM in chains of magneticatoms on the surface of a superconductor. In this talk, I will review theseries of experiments on this platform that we have performed to establish thepresence of these exotic quasi-particle using spectroscopic mapping with thescanning tunneling microscope (STM). These include the most recent study of theunique spin signature of MZM. I focus most of the talk on a new platform wherewe use the one-dimensional helical hinge states of a higher order topologicalinsulators. In particular, I will show experiment demonstrating how combinationof magnetism and superconductivity on such one-dimensional states can also giverise to MZM that can be detected with an STM. Overall these experiments,illustrate how the power of spectroscopic imaging with the STM can be used tocharacterize novel quantum states of matter and visualize their exotic quasi-particles.
Time
(Thursday) 4:00 pm - 5:00 pm
11feb4:00 pm5:00 pmMarkus TernesResearch Center Jülich, Germany4:00 pm - 5:00 pm Saturn Seminar Room
Event Details
Markus Ternes Academic Affiliation: Research Center Jülich, Germany Research Area: Understing fundamental properties on the nanoscale with the focus on magnetic excitations and correlated systems. Research stay period: February 09 - 22,
Event Details
Markus Ternes
Academic Affiliation: Research Center Jülich, Germany
Research Area: Understing fundamental properties on the nanoscale with the focus on magnetic excitations and correlated systems.
Research stay period: February 09 – 22, 2020
Talk: February 11, 16:00 – 17:00
Sensing dark spins with a scanning tunneling microscope
Probing the spin of individual atoms and molecules on surfaces by means of inelastic electron tunneling spectroscopy (IETS) has since its introduction [1] developed to a very successful and widely used method in scanning tunneling microscopy [2]. Recently, IETS measurements have been also taken simultaneously on two magnetic impurities, one attached to the apex at the tip, the other one on the sample surface, revealing correlation-driven transport asymmetries, reminiscent of spinpolarized transport in a magnetic field [3]. In this experiment only the spin on the surface was spectroscopically active while the one on the tip was spectroscopically dark.
Here now I will show how the transport is significantly altered when the tunneling electron is interacting with both spins simultaneously; the one on sample and the one on the tip apex. Different to measurements on two S = 1spins which only showed the expected steps in the differential conductance at each individual excitation and the sum of both excitations [4] we observe complex IETS data when we use a functionalized tip apex with a high S = 3/2 Kondo system to probe a S = 2 Fe adatom on the CuN surface. To successfully simulate such spectrum, Kondo as well as potential scattering processes have to be taken into account whereby strong interference effects due to the fermionic nature of the tunneling electrons lead to novel selection rules [5].
The understanding of the transport rules is important because it enables one to use well understood surface supported spins to calibrate the spin at the ill defined tip apex. Successively, such spin can then be used as a well characterized mobile sensor with unprecedented spacial resolution [6].
References:
[1] A.J. Heinrich, J.A. Gupta, C.P. Lutz, and D.M. Eigler, Science 306, 466 (2004).
[2] M. Ternes, New J. Phys. 17, 063016 (2015).
[3] M. Muenks, P. Jacobson, M. Ternes, and K. Kern, Nature Comm. 8, 14119 (2017).
[4] M. Ormaza, et al., Nano Lett. 17, 1877 (2017).
[5] M. Ternes, C.P. Lutz, A.J. Heinrich, and W.-D. Schneider, arXiv:1908.08267 [cond-mat.meshall].
[6] B. Verlhac, et al., Science 366, 623 (2019).
Time
(Tuesday) 4:00 pm - 5:00 pm
january 2020
22jan3:00 pm4:00 pmKoen BastiaansLeiden University, Netherlands3:00 pm - 4:00 pm Saturn Seminar Room
Event Details
Koen Bastiaans Academic Affiliation: Leiden University, Netherlands Research Area: Develop and use novel techniques for STM to investigate quantum matter. Talk date: January 22, 2020 A strongly inhomogeneous superfluid in an iron-based
Event Details
Koen Bastiaans
Academic Affiliation: Leiden University, Netherlands
Research Area: Develop and use novel techniques for STM to investigate quantum matter.
Talk date: January 22, 2020
A strongly inhomogeneous superfluid in an iron-based superconductor
Although the possibility of spatial variations in the superfluid of unconventional, strongly correlated superconductors has been suggested, it is not known whether such inhomogeneities – if they exist – are driven by disorder, strong scattering, or other factors. In this talk I will show how we use Josephson scanning tunneling microscopy to reveal a strongly inhomogeneous superfluid in the iron-based superconductor FeTe0.55Se0.45. By simultaneously acquiring the topographic and electronic properties, we find that this inhomogeneity in the superfluid is not caused by structural disorder or strong inter-pocket scattering, and does not correlate with variations in the energy of the Cooper pair-breaking gap. Instead, we see a clear spatial correlation between superfluid density and the quasiparticle strength, defined as the height of the coherence peak, on a local scale. [1]
References:
[1] D. Cho*, K.M. Bastiaans* et al. Nature 571, 541 (2019)
Time
(Wednesday) 3:00 pm - 4:00 pm
21jan3:00 pm4:00 pmKoen BastiaansLeiden University, Netherlands3:00 pm - 4:00 pm
Event Details
Koen Bastiaans Academic Affiliation: Leiden University, Netherlands Research Area: Develop and use novel techniques for STM to investigate quantum matter. Talk date: January 21, 2020 Charge trapping and super-Poissonian noise centers in a
Event Details
Koen Bastiaans
Academic Affiliation: Leiden University, Netherlands
Research Area: Develop and use novel techniques for STM to investigate quantum matter.
Talk date: January 21, 2020
Charge trapping and super-Poissonian noise centers in a cuprate superconductor
In this talk I will present new insight into the mystery of highly anisotropic transport in a cuprate high-temperature superconductor and show that these materials can trap additional charges. Above the superconducting transition these materials are perfectly metallic along the crystal planes (ab-plane), but are insulating in the c-axis, with ratios between in-plane and perpendicular resistance exceeding 104. This anisotropy has been identified as one of the key mysteries in the cuprates and has been connected to the mechanism of high-temperature superconductivity. I will show how we employ our newly developed scanning noise spectroscopy technique, for which we combined a scanning tunneling microscope (STM) with a novel MHz frequency amplifier to bring noise-spectroscopy measurements to the atomic scale
[1]. We discover surprisingly large deviations from the expected Poissonian noise of uncorrelated electron transport in this strongly correlated material. A behavior that is familiar from highly polarizable insulators and represents strong evidence for trapping of charge in the charge reservoir layers of the cuprates. Our measurements suggest a picture of metallic layers separated by polarizable insulators within a three-dimensional superconducting state. We will show how these new observations connect to the mystery of the anisotropic transport in this high-temperature superconductor, shedding new light onto this issue [2].
References:
[1] K.M. Bastiaans et al. Rev. Sci. Instrum. 89, 093709 (2018).
[2] K.M. Bastiaans et al. Nature Physics 14, 1183 (2018).
Time
(Tuesday) 3:00 pm - 4:00 pm
Event Details
Delegation of EU Science Counselors Date: January 20th, 2020 Time: 12:30-15:30 QNS will meet Science Counselors and Deputies of EU Countries + Switzerland and Norway. During their visit we present of our center
Event Details
Delegation of EU Science Counselors
Date: January 20th, 2020
Time: 12:30-15:30
QNS will meet Science Counselors and Deputies of EU Countries + Switzerland and Norway.
During their visit we present of our center and provide the labs tour.
More detailed schedule will be updated soon!
Time
(Monday) 12:30 pm - 3:30 pm
december 2019
16decalldaySven RoggeThe University of New South Wales, Australia(All Day: monday) KST
Event Details
Sven Rogge Affiliation: The University of New South Wales During the stay Prof. Sven Rogge will give a talk: Building Quantum Matter Atom by Atom Atomic-scale engineering reached a level of control where
Event Details
Sven Rogge
Affiliation: The University of New South Wales
During the stay Prof. Sven Rogge will give a talk:
Building Quantum Matter Atom by Atom
Atomic-scale engineering reached a level of control where single-atom devices can be reproducibly fabricated. This talk focuses on single dopant atom placement in the context of engineered matter for quantum simulation and computation. Silicon offers an interesting platform for engineered quantum matter because when isotopically purified it acts as a “semiconductor vacuum” for spins. After a general introduction of quantum simulation and computation a first step towards engineered Hamiltonians for Fermionic systems in the form of atomic chains will be presented. Here strongly interacting dopants were employed to simulate a two-site Hubbard Hamiltonian at low effective temperatures with single-site resolution which allows the quantification of the entanglement entropy and Hubbard interaction strengths. To scale this approach to larger systems in-situ multi-electrode devices have been fabricated by a scanning probe hydrogen depassivation and decoration technique. Spatially resolved gated single-electron spectroscopy maps obtained ion these devices n ultra-high vacuum will be presented. Such quantum-state images of two-donor devices led to a donor based two qubit gate design that is robust in regard to variability in dopant placement. In addition to the work on donors I will also present work on single defects in silicon with a spin-orbit interaction for electrical manipulation and coupling.
The talk will be on Monday (November 18th) from 13:00 till 14:30 in the Saturn seminar room.
Time
All Day (Monday)
Event Details
Krisztián Palotás Academic Affiliation: Wigner Research Center for Physics, Hungary Talk: December 13, 2019 First-principles-based simulation of scanning tunneling microscopy: From magnetic surfaces to molecular structures Understanding and engineering scanning tunneling microscopy (STM)
Event Details
Krisztián Palotás
Academic Affiliation: Wigner Research Center for Physics, Hungary
Talk: December 13, 2019
First-principles-based simulation of scanning tunneling microscopy: From magnetic surfaces to molecular structures
Understanding and engineering scanning tunneling microscopy (STM) image contrasts is of crucial importance in wide areas of surface science and related technologies, ranging from magnetic surfaces to molecular structures. In the talk different STM tip effects on the image contrast are highlighted based on first principles calculations, going beyond the Tersoff-Hamann model, e.g., within 3D-WKB tunneling theory [1]. Examples include highly oriented pyrolytic graphite [2], which is commonly used for STM calibration, and complex surface magnetic structures exhibiting non-collinear magnetic order, like recently popular topologically protected skyrmions [3]. By comparing STM topographic data between experiment and large scale simulations, a statistical analysis of the tip apex structure is demonstrated for the first time [2]. A combination of STM and X-ray photodiffraction helps the understanding of chirality transfer from molecules to crystal surfaces [4]. Furthermore, two recent developments of STM theories are presented: (i) an extension of Chen’s derivative rule [5] for STM simulations including tip-orbital interference effects with demonstrated importance of such effects on the STM contrast for two surface structures: N-doped graphene and a magnetic Mn2H complex on the Ag(111) surface [6]; (ii) a combined tunneling electron charge and vector spin transport theory, which provides the first steps toward the theoretical modeling of high-resolution spin transfer torque imaging [3,7].
References:
[1] K. Palotás et al., Front. Phys. 9, 711 (2014)
[2] G. Mándi et al., J. Phys.: Condens. Matter 26, 485007 (2014), Prog. Surf. Sci. 90, 223 (2015)
[3] K. Palotás et al., Phys. Rev. B 96, 024410 (2017), Phys. Rev. B 97, 174402 (2018), Phys. Rev. B 98, 094409 (2018)
[4] W. Xiao et al., Nature Chem. 8, 326 (2016)
[5] C. J. Chen, Phys. Rev. B 42, 8841 (1990)
[6] G. Mándi, K. Palotás, Phys. Rev. B 91, 165406 (2015)
[7] K. Palotás et al., Phys. Rev. B 94, 064434 (2016)
Time
(Friday) 10:00 am - 11:00 am KST
Event Details
Thomas Risse Academic Affiliation: Institute of Chemistry and Biochemistry, Freie Universität Berlin Talk: December 13, 2019 Charge transfer processes on well-defined heterogeneous model catalysts:
Event Details
Thomas Risse
Academic Affiliation: Institute of Chemistry and Biochemistry, Freie Universität Berlin
Talk: December 13, 2019
Charge transfer processes on well-defined heterogeneous model catalysts: an EPR perspective
Surfaces and their interaction with the surrounding environment play a pivotal role in a large variety of technical applications ranging from heterogeneous catalysis, coatings all the way to biological systems. Gaining insight into these systems at the atomic level is one of the key goals of today’s research, however, it is still challenging for most of the complex technological systems. With respect to heterogeneous catalysis oxides play an important role both as support material for metal nano-particles or as catalysts themselves. It is well established that much of the chemical processes at such surfaces do not happen on ideal stoichiometric low index surfaces. Instead higher index surfaces, structural defects like steps, vacancies in the lattice or thin oxide films grown on metal nano-particles -commonly referred to as the strong metal support (SMSI) effect- are important to understand the properties of the surfaces. Even though this is known for quite some time a characterization at the atomic level and an elucidation of the impact on the chemical properties is still challenging. One strategy to gain insight into these properties is using well-defined model systems which grasp essential aspects of the systems of interest but can be studied with the rigor of modern surface science methodology. In this presentation it will be shown how electron paramagnetic resonance (EPR) spectroscopy, a tool rarely used in surface science, can help to gain insight into the properties of defect sites as well as their impact on chemical and physical properties of the surfaces.
The presentation will focus on results obtained on single crystalline, epitaxial MgO oxide films grown on metal single crystal surfaces and discuss charge transfer processes that are unexpected to take place in stochiometric MgO, but become important in case paramagnetic point defects such as color center or transition metal dopants are present in the system. The role of these sites for the activation of small molecules by charge transfer will be elucidated using molecular oxygen a key ingredient for oxidation catalysis. Furthermore, it will be shown that such charge transfer processes, which are considered to be important for catalysis cannot only be induced by defect sites, but may also happen on stoichiometric oxide surfaces in case the oxide is present as an ultrathin film on a metal surface. The evidence based on EPR spectroscopy as well as tunneling microscopy for these processes and the implication of this for catalysis will be discussed.
Time
(Monday) 2:00 pm - 3:30 pm KST
november 2019
Event Details
Open Lab Day for "The World of Quantum" Art Exhibition QNS invites you to the art exhibition of quantum nanoscience. It is an collection
Event Details
Open Lab Day for “The World of Quantum”
Art Exhibition
QNS invites you to the art exhibition of quantum nanoscience. It is an collection of 44 artworks applied for a art contest “The World of Quantum”. This event also has a lab tour and networking time with QNS researchers.
Date: November 22, 2019, 16:00-17:30
Location: Room 367, Research Cooperation Building (QNS), Ewha Womans University
Event Schedule:
– “What is Quantum Nanoscience?” talk by the QNS director Andreas Heinrich.
– QNS Lab Tour: Experience the best low vibration facility in Korea.
– Introduction to the artworks of the contest: Meet the winners.
– Exhibition tour and networking with appetizers: Meet the QNS researchers.
Register to attend via the link – https://qns.science/open-lab/
Time
(Friday) 4:00 pm - 5:30 pm KST
21nov2:00 pm3:00 pmQing HuanInstitute of Physics, CAS2:00 pm - 3:00 pm KST Saturn Seminar Room
Event Details
Qing Huan Academic Affiliation: Institute of Physics, Chinese Academy of Sciences Research area: Scanning Tunneling/Probe microscopy, Specially Instrumentation Design of a bath-type cryostat and
Event Details
Qing Huan
Academic Affiliation: Institute of Physics, Chinese Academy of Sciences
Research area: Scanning Tunneling/Probe microscopy, Specially Instrumentation
Design of a bath-type cryostat and a tip-etching unit
In this talk I will mainly show a bath-type cryostat and a tip-etching unit that we designed. Detailed designing processes, like FEA (finite element analysis), circuit design, will be discussed. I will also show some of very new results from our home-made systems.
Time
(Thursday) 2:00 pm - 3:00 pm KST
Event Details
Doohee Cho Affiliation: Department of Physics, Yonsei University Research Field: Transition metal dichalcogenides, Topological insulators, Unconventional superconductors, High frequency measurements Scanning noise spectroscopy Scanning tunneling
Event Details
Doohee Cho
Affiliation: Department of Physics, Yonsei University
Research Field: Transition metal dichalcogenides, Topological insulators, Unconventional superconductors, High frequency measurements
Scanning noise spectroscopy
Scanning tunneling spectroscopy has become indispensable for investigating the local electronic structure of correlated electron systems. However, valuable information about the dynamics in electric charge transport cannot be accessed by conventional time-averaged spectroscopy techniques. An example is the granularity of charge that leads to current fluctuations; so called shot noise. Correlations can lead to deviations from Poissonian noise which are smeared out in the averaged current value. In mesoscopic systems, noise-spectroscopy measurements have been widely used to study the dynamics of strongly correlated phenomena. Here, we present a newly developed noise spectroscopy technique, for which we combine a Scanning Tunneling Microscope (STM) with a novel MHz amplifier to bring noise-spectroscopy measurements to the atomic scale. We demonstrate the Poissonian tunneling process on a Au(111) surface and the Andreev reflection induced multiple charge tunneling in a Josephson junction. In addition, we observe unexpected non-Poissonian tunneling process on a cuprate high temperature uperconductor with atomic resolution. This provides us a new way to unveil electronic properties hidden in the time-averaged transport measurements on exotic quantum materials
Time
(Wednesday) 11:00 am - 12:00 pm KST
Event Details
Christian Ast Affiliation: Max-Planck-Institute for Solid State Research, Germany Research Field: Quantum Limits in Scanning Tunneling Microscopy, Superconductivity Experimental Details of a Dilution Fridge
Event Details
Christian Ast
Affiliation: Max-Planck-Institute for Solid State Research, Germany
Research Field: Quantum Limits in Scanning Tunneling Microscopy, Superconductivity
Experimental Details of a Dilution Fridge STM
Reaching lowest temperatures in scanning tunneling microscopy (STM) requires combining the microscope with a dilution refrigerator, which triggers interesting technical. Most importantly, a dilution fridge is not a quiet piece of equipment, but STM requires the lowest noise possible. Even measuring temperature becomes a non-trivial problem. Also, the choice of materials that perform well at lowest temperatures, but are at the same time suitable for sample preparation at high temperatures is very limited. Furthermore, modeling the tunnel junction to interpret the experimental data at mK temperatures requires to go beyond the tunnel junction itself to macroscopic scales. The lower the temperature, the more the experiment becomes part of the experiment. I will discuss the challenges of building a mK-STM and interpreting the experimental data, which in the end leads to a much better understanding of the tunneling process as a whole.
Time
(Tuesday) 2:00 pm - 3:00 pm KST
Event Details
Christian Ast Affiliation: Max-Planck-Institute for Solid State Research, Germany Research Field: Quantum Limits in Scanning Tunneling Microscopy, Superconductivity Introduction to Superconductivity and Scanning Tunneling
Event Details
Christian Ast
Affiliation: Max-Planck-Institute for Solid State Research, Germany
Research Field: Quantum Limits in Scanning Tunneling Microscopy, Superconductivity
Introduction to Superconductivity and Scanning Tunneling Microscopy
Scanning tunneling microscopy (STM) is the most important experimental tool to explore the world of nanoscience due to its unique capabilities to resolve single atomic structures. STM exploits the tunneling effect to feel the topography of the sample surface at picometer length scales. Beyond the imaging functionality, the tunneling electrons themselves carry a wealth of information about the electronic properties of the substrate. This becomes particularly interesting when superconductivity is involved, because the elementary excitation in a superconductor is a Bogoliubov quasiparticle, a linear superposition of an electron and a hole, but only electrons or holes can tunnel. I will give an introduction to the basics of tunneling in the STM with a particular focus on tunneling between superconductors.
Time
(Monday) 2:00 pm - 3:00 pm KST
06nov4:00 pm5:00 pmJacob RepickyThe Ohio State University4:00 pm - 5:00 pm KST Saturn Seminar Room
Event Details
Jacob Repicky Academic Affiliation: The Ohio State University Research Area: Low-Temperature Scanning Tunneling Microscopy Magnetic Textures in Chiral Magnet MnGe Observed with SP-STM Materials with
Event Details
Jacob Repicky
Academic Affiliation: The Ohio State University
Research Area: Low-Temperature Scanning Tunneling Microscopy
Magnetic Textures in Chiral Magnet MnGe Observed with SP-STM
Materials with non-centrosymmetric crystal structures can host chiral spin states including magnetic skyrmions. Bulk MnGe hosts a short period magnetic state (3 nm), whose structure depends strongly on atomic lattice strain, and shows a large emergent transport signature associated with the skyrmion phase. Here, we use low-temperature (5 K) spin-polarized scanning tunneling microscopy (SP-STM) to image the magnetic textures in MnGe thin films grown via molecular beam epitaxy and study the influence of the surface on those textures. Most microscopic locations show a spin spiral phase with a 6-8 nm period and a propagation direction that is influenced by step edges, surface termination, and strain. We also report the presence of isolated target skyrmions that likely form due to local modulations in the atomic structure. The skyrmions have a triangular shape which appears to be set by the in-plane lattice vectors, and a core size of approximately 15 nm. We observe the target state is significantly more sensitive to magnetic fields than the spiral phase, and that local voltage and current pulses with the STM tip imply the texture can be ‘switched’ between states with different topological charge. To fully understand the magnetic textures in MnGe we will expand this study by investigating films of different thicknesses to vary the magnetic anisotropy.
Time
(Wednesday) 4:00 pm - 5:00 pm KST
october 2019
Event Details
Yu Wang Affiliation: Tohoku University, Sendai, Japan Scanning Tunneling Micrososcopy(STM) Study of Supramolecule Formation and Spin Properties of Radical Molecules of Cobalt Tetrakis(1,2,5-thiadizole)
Event Details
Yu Wang
Affiliation: Tohoku University, Sendai, Japan
Scanning Tunneling Micrososcopy(STM) Study of Supramolecule Formation and Spin Properties of Radical Molecules of Cobalt Tetrakis(1,2,5-thiadizole) Porphyrazine(CoTTDPz) and 1,3,5-Trithia-2,4,6-Triazapentalenyl(TTTA)
Organic molecule films adsorbed on metal substrates have been widely reported because of the potential application on electronic devices. In this context, metallo-phthalocyanines (MPcs) and their derivatives are intensively studied. However, most of related works above are based on weak molecule-molecule interaction system while a series of Pc derivatives with strong intermolecular force have been synthesized, called metallo-tetrakis(1,2,5-thiadiazole) porphyrazines (MTTDPz). LT-STM study of CoTTDPz on Au(111) from sub-monolayer to multilayer will be introduced in this talk. Image and STS are applied to characterize the bonding configuration and electronic properties of molecules. In addition, the spin properties of CoTTDPz have been studied by detecting Kondo feature on molecules, which show different behaviours form CoPc.
STM observation of TTTA on Au(111) is also described. It belongs to heterocyclic π-radicals family which have been widely studied in recent years, because of the reversible process that the dimers are disposed to thermally driven dimer (S=0) to radical (S=1/2). In my experiment, coverage of TTTA is controlled by adjusting exposing time and annealing. When coverage is near 1 monolayer, two types of TTTA-Au coordination are confirmed and both of them have chirality, electrostatic bonding was also observed in lattice which only appeared between two identical arrays. At low coverage, hierarchical structures made up by threefold units were dominating, the height of Au adatoms are higher than those in arrays. While the mixture of the two structures occurred without initial annealing, this work was probably the first real space observation of TTTA.
Time
(Tuesday) 10:00 am - 11:30 am KST
Event Details
Stefano Agrestini Affiliation: ALBA Synchrotron Light Source, Barcelona, Spain Research Field: Electronic and magnetic ground state of spin-orbit active transition metal compounds using
Event Details
Stefano Agrestini
Affiliation: ALBA Synchrotron Light Source, Barcelona, Spain
Research Field: Electronic and magnetic ground state of spin-orbit active transition metal compounds using x-ray spectroscopy (XAS, XMCD, RIXS)
Introduction to multiplet theory
The first part of the lecture will deal with the theory of full atomic multiplet interaction and its effect on the lineshape of the XAS spectrum. The term symbols will be introduced in order to properly describe the ground state and the final states that can be reached in the absorption process. In the second part the crystal field and ligand field theories will be introduced in order to properly describe the L2,3 spectra of transition metal compounds. Examples of orbital degeneracy breaking induced by the crystal field and its effect on the ground state symmetry will be shown.
Time
(Tuesday) 10:00 am - 11:30 am KST
Event Details
Stefano Agrestini Affiliation: ALBA Synchrotron Light Source, Barcelona, Spain Research Field: Electronic and magnetic ground state of spin-orbit active transition metal compounds using
Event Details
Stefano Agrestini
Affiliation: ALBA Synchrotron Light Source, Barcelona, Spain
Research Field: Electronic and magnetic ground state of spin-orbit active transition metal compounds using x-ray spectroscopy (XAS, XMCD, RIXS)
Introduction to x-ray absorption spectroscopy and x-ray magnetic circular dichroism
The lecture will first provide a general introduction to the absorption process and the methods used to measure an x-ray absorption spectrum (XAS). I will present the key features that makes this technique so powerful and simple examples of the variety of information about the local electronic and magnetic structure that can be determined from XAS. In the second part I will discuss the spectral shape of XAS and the need of a multielectron approach to describe it. Finally, I will explain the application of the sum rules to x-ray magnetic circular dichroism (XMCD) data in order to determine the spin and orbital moments. Examples of experimental studies using XMCD will be shown.
Time
(Monday) 1:00 pm - 2:00 pm KST
Event Details
Tyler Cocker Affiliation: Michigan State University, USA Seminar Time: October 4th, 2019, 11:00-12:00 Ultrafast terahertz scanning tunneling microscopy of atomically precise nanostructures Terahertz scanning tunneling
Event Details
Tyler Cocker
Affiliation: Michigan State University, USA
Seminar Time: October 4th, 2019, 11:00-12:00
Ultrafast terahertz scanning tunneling microscopy of atomically precise nanostructures
Terahertz scanning tunneling microscopy (THz-STM) is a new ultrafast imaging technique that provides access to femtosecond dynamics on the atomic scale for the first time. Its versatility enables numerous scientific opportunities, including ultrafast studies of electron dynamics within single molecules and nanostructures. In this talk, I will introduce a conceptual basis for ultrafast terahertz scanning tunneling spectroscopy, show THz-STM snapshot imaging of local electron densities, and discuss future directions in the field.
Time
(Friday) 11:00 am - 12:00 pm KST
september 2019
Event Details
International IBS Conference on Quantum Nanoscience Date: September 25 - 27, 2019 Location: Lee SamBong Hall, ECC Building, Center for Quantum
Event Details
International IBS Conference on Quantum Nanoscience
Date: September 25 – 27, 2019
Location: Lee SamBong Hall, ECC Building, Center for Quantum Nanoscience at Ewha Womans University in Seoul, South Korea
There are many conferences that cover subfields of this research area but as far as the organizers know, this is the first conference that attempts to bring researchers in the broader field of quantum nanoscience together as one community.
Visit https://icqns.org/ to learn more about our conference.
Time
25 (Wednesday) 9:00 am - 27 (Friday) 6:00 pm
Event Details
Deung-Jang Choi Affiliation: Centro de Física de Materiales (CSIC-UPV/EHU) Talk: September 17, Tue 11:00~12:00 Research Field: Nanomagnetism combined with superconductivity Spin chains on surfaces Scanning tunneling
Event Details
Deung-Jang Choi
Affiliation: Centro de Física de Materiales (CSIC-UPV/EHU)
Talk: September 17, Tue 11:00~12:00
Research Field: Nanomagnetism combined with superconductivity
Spin chains on surfaces
Scanning tunneling microscopy (STM) has proved to be a mature technique for the study of magnetic impurities on different substrates. STM allows us to manipulate the atoms and assemble magnetic structures of atomic dimensions that are going to behave differently depending on their geometrical and chemical composition. We
build the chains in such that form a highly correlated spin doublet ground state exhibiting a Kondo resonance. Recently, the introduction of new impurity states in the superconducting gap has received a lot of attention. Magnetic adatoms can be considered as impurities that weaken the binding of superconducting Cooper pairs leading to impurity levels in the gap: so-called Yu-Shiba-Rusinov (YSR) states. By applying our STM techniques to the study of magnetic spectra on superconducting surfaces, we reveal the orbital properties of the YSR states associated with the magnetic impurities. The influence of the atoms on the superconducting electronic structure is revealed as well as the interactions at work. Such magnetic impurities on different substrates allow us to explore many-body effects and exotic phenomena in different experimental spin systems giving an understanding on the parameters on each system.
Time
(Tuesday) 11:00 am - 12:00 pm KST
august 2019
21aug11:00 am12:00 pmKatharina J. FrankeFreie Universität Berlin11:00 am - 12:00 pm KST
Event Details
Katharina J. Franke Affiliation: Freie Universität Berlin Research Field: Scanning Tunneling Microscopy of magnetic adatoms on superconductors, Molecules on surfaces Talk: August 21, 11:00
Event Details
Katharina J. Franke
Affiliation: Freie Universität Berlin
Research Field: Scanning Tunneling Microscopy of magnetic adatoms on superconductors, Molecules on surfaces
Talk: August 21, 11:00 -12:00
Transport properties through Shiba states
Magnetic adsorbates on conventional s-wave superconductors lead to exchange interactions that can induce bound states inside the superconducting energy gap. These states are known as YuShiba-Rusinov states (or Shiba states) and can be resolved by scanning tunneling spectroscopy as a pair of resonances at positive and negative bias voltages in the superconducting gap. Here, we employ tunneling spectroscopy at 1.1 K to investigate magnetic atoms on a superconducting Pb surface. The single-atom junctions are stable over several orders of magnitude in conductance. We observe two different transport regimes: at large tip-sample distance, the tunneling current is dominated by single-electron processes. However, these require the relaxation of electrons/holes from the Shiba states into the superconductor. At small tip-sample distance, the relaxation processes are not sufficiently fast for an efficient depopulation of the states, and thus Andreev processes become important, which resonantly transfer a Cooper pair into the superconductor. We probe the nature of the two-electron transport processes by irradiating the junction with microwaves from an antenna placed close to the junction. The tunneling electrons absorb or emit photons from the microwave field resulting in a distinct pattern of split Shiba states as a function of irradiation power.
Time
(Wednesday) 11:00 am - 12:00 pm
14aug1:00 pm2:00 pmKatharina J. FrankeFreie Universität Berlin1:00 pm - 2:00 pm KST
Event Details
Katharina J. Franke Affiliation: Freie Universität Berlin Research Field: Scanning Tunneling Microscopy of magnetic adatoms on superconductors, Molecules on surfaces Talk: August 14, 13:00
Event Details
Katharina J. Franke
Affiliation: Freie Universität Berlin
Research Field: Scanning Tunneling Microscopy of magnetic adatoms on superconductors, Molecules on surfaces
Talk: August 14, 13:00 -14:00
Tuning the exchange and potential scattering strength of individual magnetic adsorbates on superconductors
Magnetic impurities in conventional superconductors induce a pair-breaking potential, which leads to bound states inside the superconducting energy gap. These states are called Yu-Shiba-Rusinov states, or short: Shiba states, and can be probed by scanning tunneling spectroscopy at the atomic scale. The energy of these states depends on the strength of both exchange and potential scattering. Here, we explore different strategies to tune the energy of the Shiba states. In the first case, we tune the strength of the magnetic exchange scattering to the Cooper pairs. Upon tip approach we are able to continuously vary the energy of Shiba states induced by Fe-porphin molecules on Pb(111) across the Fermi energy. This model system further allows to study the quantum phase transition between a screened and unscreened spin. In the second case, we make use of the charge-density wave (CDW) of NbSe2, which coexists with superconductivity, to tune the energy of Shiba states of individual Fe atoms. All atoms are placed in the same atomic adsorption site, but at different positions with respect to the CDW. The Shiba states exhibit different energies and different oscillatory patterns. We ascribe the shift in energies to the variation of the density of states as well as to changes in the potential scattering strength.
Time
(Wednesday) 1:00 pm - 2:00 pm
12aug2:00 pm3:00 pmHerve AubinCNRS - University Paris-Saclay2:00 pm - 3:00 pm KST
Event Details
Herve Aubin Affiliation: CNRS - University Paris-Saclay Talk: August 12th,2019 Research Field: STM - spectroscopy, Quantum effects on superconductivity Hybrid semiconducting-superconducting systems and superconductivity at
Event Details
Herve Aubin
Affiliation: CNRS – University Paris-Saclay
Talk: August 12th,2019
Research Field: STM – spectroscopy, Quantum effects on superconductivity
Hybrid semiconducting-superconducting systems and superconductivity at the Anderson limit
Hybrid semiconducting-superconducting systems have attracted intense interest because of their potential applications to the fields of superconducting spintronic and topological superconductivity. After a brief overview of hybrid superconducting-semiconducting systems, including some recent works in our group [1,2], I will present a scanning tunneling spectroscopy study of superconducting lead (Pb) nanocrystals grown on the (110) surface of InAs.
The existence of Cooper pairing and the nature of superfluid order in clusters with a small number of Fermions are questions of fundamental interest that have implications for various systems, from atomic nucleus to Helium clusters and superconducting nanocrystals. With its atomic resolution capabilities, STM is an ideal instrument for the study of the electronic spectrum of small size superconducting nanocrystals. Yet, so far, such studies have been hampered by the two antagonistic requirements that the substrate must be conducting and the nanocrystals only weakly coupled to this substrate.Instead of a simple metallic substrate, we found that the 2D electron gas of large Fermi wavelength at the surface of InAs provides an ideal substrate for the growth and study of superconducting lead (Pb) nanocrystals in the regime of quantum confinement.
This discovery allowed to study, for the first time by STM, the superconducting parity effect in nanocrystals as function of their volume and to demonstrate unambiguously the validity of the Anderson criterion, conjectured in 1959, for the existence of superconductivity in nanocrystals submitted to quantum size effects [3].
References:
1. Assouline, A. et al. Spin-Orbit induced phase-shift in Bi2Se3 Josephson junctions.
Nat. Commun. 10, 126 (2019).
2. Assouline, A. et al. Shiba Bound States across the Mobility Edge in Doped InAs Nanowires.
Phys. Rev. Lett. 119, 097701 (2017).
3. Vlaic, S. et al. Superconducting parity effect across the Anderson limit.
Nat. Commun. 8, 14549 (2017).
Time
(Monday) 2:00 pm - 3:00 pm
09aug11:00 am12:00 pmRomain StompZurich Instruments AG11:00 am - 12:00 pm KST
Event Details
Romain Stomp Affiliation: Zurich Instruments AG Talk: August 9, 2019 Research Field: Scanning Probe Microsopy, Digital Signal Processing Smart versus Big Data in SPM: from
Event Details
Romain Stomp
Affiliation: Zurich Instruments AG
Talk: August 9, 2019
Research Field: Scanning Probe Microsopy, Digital Signal Processing
Smart versus Big Data in SPM: from frequency to time domain analysis
Non-linearity or transient phenomena in Scanning Probe Microscopy (SPM) tip-sample interaction are responsible for large deviations in simple harmonic oscillator models that necessitate various multifrequency techniques or timeresolved analysis. By now, many different methods of data deconvolution have been used, some of which may be platform dependent to a single SPM manufacturer. In this talk, I would like to focus on smart and universal data acquisition using FPGA-based hardware and server-based software, which can work with any third-party instruments. Both time and frequency domain analysis can then be performed in realtime or streamed to a usable data set for further calculation. The aim is to either crunch down data to its essential components using lock-in techniques in open or closed loops or to accurately align large digitized data streams in a useable matrix format [1]. The ability to bring Arbitrary Waveform Generator (AWG) in the SPM path allows for precise control of delays for either pure electrical pump-probe approach or in combination with optical methods [2]. Extension of this to the manipulation of qubit state will also be addressed.
References:
[1] Ehsan Nasr Esfahani, PhD dissertation, University of Washington, Seatle, 2018
[2] Time-resolved SPM
Time
(Friday) 11:00 am - 12:00 pm
july 2019
Event Details
Sungmin Kim Affiliation: National Institute of Standards and Technology, MD, United States Talk: July 4, 2019 Improvement of milli-Kelvin Scanning Probe Microscope System and
Event Details
Sungmin Kim
Affiliation: National Institute of Standards and Technology, MD, United States
Talk: July 4, 2019
Improvement of milli-Kelvin Scanning Probe Microscope System and Edge State Studyof Graphene Quantum Hall Device
In this talk, I present the improvement of functionality and energy resolution of tunneling spectroscopy of the NIST milliKelvin SPM system, and recent studies performed by this system on graphene quantum Hall device. The NIST millikelvin SPM system was constructed in 2010 as the first generation of millikelvin STM by using dilution refrigerator, and it has been operated to conduct the number of researches on 2D materials such as graphene, topological insulators. Recently, implementation of qPlus sensor AFM on the SPM module made it overcome the limitation of tunneling current measurement. By applying multi-contact sample holder and auto navigating algorithm we accomplished the in-situ transport measurement. In addition, by combining RF filters and proper electrical grounds, we achieved an ultra-high energy resolution tunneling spectroscopy – better than 10ueV energy resolution – for measuring Josephson peak spectrum on superconductor-superconductor junction, which is the best level of energy resolution in tunneling spectroscopy measurement by using SPM so far. For the analysis of high energy resolution spectroscopy, P(E) model and Maki’s theory are applied. In addition, recent studies of graphene quantum Hall edge state by AFM and KPFM measurements will be introduced.
The information about time and location of the talk will be updated soon.
Time
(Thursday) 1:00 pm - 2:00 pm
Event Details
Kyung Soo Choi Affiliation: Institute for Quantum Computing/University of Waterloo & the Perimeter Institute for Theoretical Physics Talk: July 1, 2019 Many-body quantum electrodynamics (QED) with atoms and photons: A new platform
Event Details
Kyung Soo Choi
Affiliation: Institute for Quantum Computing/University of Waterloo & the Perimeter Institute for Theoretical Physics
Talk: July 1, 2019
Many-body quantum electrodynamics (QED) with atoms and photons: A new platform for quantum optics
An exciting frontier in quantum information science is the creation and manipulation of quantum systems that are built and controlled quanta by quanta. In this context, there is an active research worldwide to achieve strong and coherent coupling between light and matter as the building block of complex quantum systems. Despite the range of physical behaviours accessible by these QED systems, the low-energy description is inherently masked by mean fields or renormalization groups
In contrast, I describe our comprehensive theory/experiment program towards synthetic quantum matter, where highly-correlated Rydberg quantum material is strongly coupled to quantized optical cavity fields. We call this new domain of quantum optics, “many-body quantum electrodynamics,” where locally gauged quantum materials are entirely driven by quantum optical fluctuations. I describe our initial laboratory effort towards stabilizing a 2D U(1) quantum spin liquid and the observation of cavity-mediated multiparticle plaquette dynamics, corresponding to an emergent visonic topological defect excitation, for the magnetic flux of the compact dynamical gauge field.
From a broader perspective, our work towards many-body QED will open exhilarating opportunities in atomic and condensed matter physics, and quantum information science to explore the consequential features of macroscopic universes living within strongly-correlated systems, and to help answer some of the most profound questions in physics and computer science — from Baryonic asymmetry, to quantum gravity, and to the quantum Church-Turing thesis. We believe that many-body QED is an essential endeavour for our very instinct to explore genuinely surprising phenomena arising from highly-entangled quantum matter, by light.
Time
(Monday) 1:00 pm - 2:00 pm
june 2019
14jun1:00 pm2:00 pmQing HuanInstitute of Physics, Chinese Academy of Sciences1:00 pm - 2:00 pm KST
Event Details
Qing Huan Academic Affiliation: Institute of Physics, Chinese Academy of Sciences Research area: Scan tunneling/probe microscopy, specially instrumentation Visit Dates: June 13, 2019 Recent R&D
Event Details
Qing Huan
Academic Affiliation: Institute of Physics, Chinese Academy of Sciences
Research area: Scan tunneling/probe microscopy, specially instrumentation
Visit Dates: June 13, 2019
Recent R&D progresses on UHV SPM in IOP, CAS – Components and systems
This talk will mainly focus on instrumentation. I will introduce our R&D progresses on UHV-SPM systems and related components, which includes evaporators, electronics, cryostat, scanner heads, the update of a 4-probe STM, Variable-temperature STM, Low-temperature SPM combined with MBE and optical accesses, and Low-temperature STM combined with Combi-LMBE et. al. Some of the test results and research results from these systems will also be shown.
Time
(Friday) 1:00 pm - 2:00 pm
12jun1:00 pm2:00 pmEster NijrolderRadboud University Nijmegen1:00 pm - 2:00 pm KST
Event Details
Ester Nijrolder Academic Affiliation: Radboud University Nijmegen Research area: STM - spectroscopy, quantum effects on superconductivity Visit Dates: June 9 - 15, 2019 Coupled atom
Event Details
Ester Nijrolder
Academic Affiliation: Radboud University Nijmegen
Research area: STM – spectroscopy, quantum effects on superconductivity
Visit Dates: June 9 – 15, 2019
Coupled atom magnetism
In modern times more and more technology is used during the day. All this technology is based on logic operators that work with electric currents. One of the ways to make these logic operators more energy efficient is to make magnetic logic operators. But, to make magnetic logic operators applicable in everyday life, we still need to learn a lot about them. Therefore I’m giving a summary of different types of coupled atom magnetism on surfaces, which eventually could be used to make logic operators consisting of only a few atoms. This is an improvement in both size and energy efficiency, but there is still a long way to go.
Time
(Wednesday) 1:00 pm - 2:00 pm
Event Details
Joint Workshop IBS CNM-QNS Talks: June 7, 2019 16:00 - 16:20 - Taeyoung Choi "Single atom electron spin resonance toward atomic
Event Details
Joint Workshop IBS CNM-QNS
Talks: June 7, 2019
16:00 – 16:20 – Taeyoung Choi “Single atom electron spin resonance toward atomic scale quantum sensor”
16:25 – 16:45 – Kwanpyo Kim “Atomic Structures and E-Beam-Induced Dynamics of 2D van der Waals Heterostructures”
16:55 – 17:10 – IBS CNM – QNS Casual Meeting
Time
(Friday) 4:00 pm - 5:30 pm KST
07jun1:30 pm2:30 pmFranklin ChoCenter for Quantum Nanoscience1:30 pm - 2:30 pm KST
Event Details
Franklin Cho Talk: June 7, 2019 High-frequency (HF) electron spin resonance (ESR) spectroscopy and ESR based quantum computing Electron spin resonance (ESR)
Event Details
Franklin Cho
Talk: June 7, 2019
High-frequency (HF) electron spin resonance (ESR) spectroscopy and ESR based quantum computing
Electron spin resonance (ESR) spectroscopy is a powerful and versatile tool for probing and studying local structures and dynamic properties of various compounds in liquids and solids; for example, structures and dynamics in biological molecules, magnetic structures and relaxations in magnetic molecules and quantum coherence in solid-state spin systems.
High-frequency (HF) ESR spectroscopy is an emerging technique enabling finer spectral resolution, better absolute sensitivity, and improved time resolution. I will first talk about the development of a HF ESR spectrometer at the University of Sothern California [1,2]. The spectrometer consisting of a high-power HF solid-state source, a quasioptical system, a phase-sensitive superheterodyne detection system, a 12.1 Tesla cryogenic-free superconducting magnet, and a 4He cryostat enables pulsed ESR measurements with a few hundred nanosecond pulses. I will also discuss some of its unique experimental capabilities such as double electron-electron resonance and dynamical decoupling to study paramagnetic impurities existing in synthetic diamond crystals.
If time permits, I will then talk about our efforts on ESR based quantum computing at the University of Waterloo, particularly experimental realization of a quantum algorithm known as heat-bath algorithmic cooling using a solid-state electron-nuclear coupled system [3]. A home-built pulsed X-band ESR spectrometer with arbitrary waveform generator is employed (electron-nuclear double resonance capability was added later) [4]. Major focus has been understanding noises and improving quantum control which is critical in the field of quantum computing and quantum information processing [5,6].
[1] F. H. Cho, V. Stepanov, and S. Takahashi, Review of Scientific Instruments 85, 075110 (2014).
[2] F. H. Cho, V. Stepanov,C. Abeywardana, and S. Takahashi, Methods in Enzymology 563, 95 (2015)
[3] D. K. Park, G. Feng, R. Rahimi, S. Labruyère, T. Shibata, S. Nakazawa, K. Sato, T. Takui, R. Laflamme, and J. Baugh, Quantum Information Processing 14, 2435 (2015)
[4] D. K. Park, G. Feng, R. Rahimi, J. Baugh, and R. Laflamme, Journal of Magnetic Resonance 267, 68 (2016)
[5] G. Feng, J. J. Wallman, B. Buonacorsi, F. H. Cho, D. K. Park, T. Xin, D. Lu, J. Baugh, and R. Laflamme, Physical Review Letters 117, 260501 (2016)
[6] G. Feng, F. H. Cho, H. Katiyar, J. Li, D. Lu, J. Baugh, and R. Laflamme, Physical Review A 98, 052341 (2018)
Time
(Friday) 1:30 pm - 2:30 pm
05jun11:00 am12:00 pmKarina MorgensternRuhr-Universität Bochum11:00 am - 12:00 pm KST
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Karina Morgenstern Academic Affiliation: Ruhr-Universität Bochum Research area: Surface Science Visit Dates: June 5, 2019 STM investigation of laser driven processes at surfaces While
Event Details
Karina Morgenstern
Academic Affiliation: Ruhr-Universität Bochum
Research area: Surface Science
Visit Dates: June 5, 2019
STM investigation of laser driven processes at surfaces
While photochemistry in the gas phase demands a resonant excitation of the molecules, the presence of a metal surface in surface chemistry opens a different pathway via the creation of hot electrons in the metal and subsequent attachment of these energetic electrons to adsorbed molecules. We use two set-ups that combine a low-temperature scanning tunneling microscope operating below 10 K with a frequency doubled femto-second laser and a tunable pico-second laser, respectively, to investigate processes induced by these electrons on a single molecule basis.
In this talk, I will first present recent results on the effect of intense fs-laser illumination on the structure of metal surfaces, in particular Ag(100) and Cu(111). Then I will compare laser-induced diffusion to thermal diffusion of CO molecules on Cu(111). In particular the long-range interaction between diffusing molecules differs in the two cases. Finally, I will present results obtained by electrons attaching to and solvating in different ice structures adsorbed on Cu(111) without and with halogenated (chlorine or bromine) benzene molecules adsorbed on them. These model systems enhance our understanding of the impact of ionizing radiation on the chemical composition of Earth’s upper atmosphere (e.g. its ozone density), which is known to trigger chemical processes at the surfaces of cold ice covered grain particles.
Time
(Wednesday) 11:00 am - 12:00 pm
04jun4:00 pm5:00 pmKarsten ReuterTechnische Universität München4:00 pm - 5:00 pm
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Karsten Reuter Academic Affiliation: Technische Universität München Prof. Reuter’s (b. 1970) research activities are mainly focused on quantitative modeling of material
Event Details
Karsten Reuter
Academic Affiliation: Technische Universität München
Prof. Reuter’s (b. 1970) research activities are mainly focused on quantitative modeling of material properties and functionalities. Heterogeneous catalysis is a particular area of interest. He makes widespread use of modern multiscale modeling, which unites methods and concepts from the disciplines of physics and chemistry as well as materials science and engineering.
Talk: June 4, 2019
Knowledge-Based Approaches in Catalysis and Energy Modelling
Reflecting the general data revolution, knowledge-based methods are now also entering theoretical catalysis and energy related research with full might. Automatized workflows and the training of machine learning approaches with first-principles data generate predictive-quality insight into elementary processes and process energetics at undreamed-of pace. Computational screening and data mining allows to explore these data bases for promising materials and extract correlations like structure-property relationships. At present, these efforts are still largely based on highly reductionist models that break down the complex interdependencies of working catalyst and energy conversion systems into a tractable number of so-called descriptors, i.e. microscopic parameters that are believed to govern the macroscopic function. For certain classes of materials like transition metal catalysts, corresponding human-designed models have indeed established trend understanding and spurred a targeted materials design. Future efforts will concentrate on using artificial intelligence also in the actual generation and reinforced improvement of the reductionist models. This is expected to better capture complexities like incomplete understanding or operando changes of interfacial morphology, to provide access to structured and compound materials classes, or ultimately to even fulfill the dream of an inverse (de novo) design from function to structure. In this talk, I will briefly survey these developments, providing examples from our own research, in particular on adsorption energetics at bimetallic catalysts and data mining for the design of organic semiconductors.
Time
(Tuesday) 4:00 pm - 5:00 pm
may 2019
Event Details
Theory Workshop "Quantum Spins at the Nanoscale" Date: May 27 - 30, 2019 Location: Center for Quantum Nanoscience at Ewha Womans University in Seoul, South
Event Details
Theory Workshop “Quantum Spins at the Nanoscale”
Date: May 27 – 30, 2019
Location: Center for Quantum Nanoscience at Ewha Womans University in Seoul, South Korea
The workshop Quantum Spins at the Nanoscale: Recent Theoretical Advances will bring together international experts in the field of Quantum Nanoscience in Ewha Womans University (Korea) between May 27th and 30th 2019 to stimulate discussion and foster collaborations about emerging physics of Quantum Systems from a theoretical perspective.
Description:
The workshop Quantum Spins at the Nanoscale: Recent Theoretical Advances will focus on recent developments in the study of open quantum spin systems at the nanoscale where coherence, interactions and topology play an important role.
With the recent development of quantum materials and spin control, it becomes possible to emulate and reveal new complex and intriguing quantum phenomena both at equilibrium but also in the non-equilibrium by driving the systems. Quantum spin control also allows to address fundamental issues related to quantum information theory and spin-based quantum computing.
Time
27 (Monday) 9:00 am - 30 (Thursday) 6:00 pm KST
16may3:00 pm3:30 pmAndreas HeinrichSeoul Forum3:00 pm - 3:30 pm KST Vista Walkerhill Seoul
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Your browser does not support the video tag Andreas Heinrich Seoul Forum Session 3 Break Down the
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Andreas Heinrich
Seoul Forum
Session 3 Break Down the Wall – Creativity and Communication
Talk: May 16, 2019, 15:00 ~ 15:30
From Quantum Nanoscience to ‘the Boy and his Atom’
Basic science has become a crucial element for the future success of the Korean economy. In order to promote world-class basic science research, Korea recently created the Institute for Basic Science. In this lecture, we will briefly introduce the research performed at the Center for Quantum Nanoscience, which has the potential to lay the foundation for future quantum technologies, such as quantum computation. Rather than focusing mostly on the science, in this presentation we will discuss why it is of crucial importance to communicate well with a general audience. Nowadays we have many tools at our disposal primarily based on social media, such as YouTube, Facebook and Naver. I will describe my experience at creating engaging content that can draw members of a general audience to science and entice them to ask deep question in a fun environment. Besides social media, this year my team at the Center for Quantum Nanoscience is reaching out to the art community to create the art of quantum and nanoscience – again with the primary goal of engaging a non-scientific audience in the complex and fascinating ideas of this research field.
Time
(Thursday) 3:00 pm - 3:30 pm KST
april 2019
15apr1:30 pm2:30 pmSee-Hun YangIBM Research – Almaden1:30 pm - 2:30 pm KST
Event Details
See-Hun Yang Academic Affiliation: IBM Research – Almaden Talk: June 4, 2019 Chiral Spintronics Chirality is one of the fundamental asymmetries in nature.
Event Details
See-Hun Yang
Academic Affiliation: IBM Research – Almaden
Talk: June 4, 2019
Chiral Spintronics
Chirality is one of the fundamental asymmetries in nature. Objects with chirality cannot be superimposed onto each other after mirror reflection operation like right and left hands. Archetypal examples of chiral objects are chiral molecules in stereroisomers and chiral magnetic domain walls whose chiralities are set by e.g. Dzyaloshinskii-Moriya interaction. Most importantly moving spins become chiral such that they can reciprocally interact with chiral objects thus allowing “Chiral Spintronics”. This means that spins traveling in a chiral object can be polarized or reversely spin angular momentum can be transferred to the chiral structure. In this talk I will review this emerging new field, the marriage of spintronics to chirality, by discussing recently discovered various novel torques and phenomena from chiral magnetic nanostructures to chiral molecules: spin-orbit torques from perpendicularly magnetized ultrathin films [1], exchange coupling torque [2] and novel new phase of domain wall dynamic, chiral exchange drag [3] from synthetic antiferromagnets, and efficient separation of chiral molecules, enantiomers, by magnetic structure [4]. In the end I will give an overall outlook on Chiral Spintronics and discuss potential applications from the new findings.
[1] K.-S. Ryu, L. Thomas, S.-H. Yang, and S. S. P. Parkin, “Chiral spin torque at magnetic domain walls”, Nat. Nano. 8, 527 (2013).
[2] S.-H. Yang, K.-S. Ryu, and S. S. P. Parkin, “Domain-wall velocities of up to 750 m s−1 driven by exchange-coupling torque in synthetic antiferromagnets“, Nat. Nano. 10, 221 (2015).
[3] S.-H. Yang, C. Garg, and S. S. P. Parkin, “Chiral Exchange Drag and Chirality Oscillations in Synthetic Antiferromagnets”, Nature Physics 10.1038/s41567-019-04383 (2019).
[4] K. Banerjee-Ghosh, O.B. Dor, F. Tassinari, E. Capua, S. Yochelis, A. Capua, S.-H. Yang, S.S.P. Parkin, S. Sarkar, L. Kronik, L. T. Baczewski, R. Naaman, and Y. Paltiel, “Separation of enantiomers by their enantiospecific interaction with achiral magnetic substrates”, Science 360, 1331 (2018).
Time
(Monday) 1:30 pm - 2:30 pm
03apr1:00 pm2:00 pmJin Kyung Kim "The World of Quantum"Ewha Womans University1:00 pm - 2:00 pm
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Jin Kyung Kim Academic Affiliation: Ewha Womans University Talk: April 3, 2019 The World of Quantum Come and learn where quantum nanoscience and art
Event Details
Jin Kyung Kim
Academic Affiliation: Ewha Womans University
Talk: April 3, 2019
The World of Quantum
Come and learn where quantum nanoscience and art meet at our contest kick-off talk on ‘The World of Quantum’. This talk is specifically towards artists and does not require any scientific background. The subject of the art contest is quantum nanoscience.
Let us shrink down to the nanometer scale. If you shrink even more and go into an atom it becomes the quantum world. Things that are impossible in our daily life happen in that space. You can be in two places at once or pass through walls. You can be both alive and dead. Use your imagination to express the quantum world!
Time
(Wednesday) 1:00 pm - 2:00 pm
march 2019
Event Details
Joint Workshop IBS CNM-QNS Talks: March 20, 2019 16:00 - 16:20 - Jae-Hyun Lee "Nano-Bio Interface and Local Interfacing of Nanodevice
Event Details
Joint Workshop IBS CNM-QNS
Talks: March 20, 2019
16:00 – 16:20 – Jae-Hyun Lee “Nano-Bio Interface and Local Interfacing of Nanodevice on Neuronal Cells”
Prof. Jae-Hyun Lee’s major interest of research is nanoscale probe design for biology and medicine. More specifically, fabrication of nanobioelectronic devices, interfacing nanodevice and biological system in single cellular level, development of nano-actuator and imaging probes, and nanomedicine for diagnosis and therapeutics are the focus of his research. Lee has published several seminal works in nanomedicine and has been recognized by the community. He was the first-place awardee of Nanotechnology Young Researcher Award of IOP Publishing in 2015. He was also highlighted in Donga-Ilbo one of leading Korea Newspaper Companies, as the most cited Korean Scientist in medicine in 2016.
16:25 – 16:45 – Fabio Donati “A magnetic bit made of a single atom”
Prof. Fabio Donati will show that rare earth atoms exhibit magnetic stability on the timescale of hours when adsorbed on ultra-thin oxide film grown on a metal substrate. First, he will summarize the techniques that has been used to pioneer this rapidly evolving field, and the sequence of breakthroughs that led to the discovery of single atom magnets. Then, he will present the unconventional properties of the first discovered single atom magnet, namely a holmium atom adsorbed on a magnesium oxide ultra-thin film. These atoms exhibit magnetic stability, with a spin lifetime of 1500 s at 10 K and a magnetic hysteresis up to 40 K [4,5,6]. Finally, he will conclude presenting the research in this field that his team is currently carrying out at the IBS Center for Quantum Nanoscience of the Ewha Womans University.
16:55 – 17:10 – IBS CNM – QNS Casual Meeting
Time
(Wednesday) 4:00 pm - 5:30 pm KST
Event Details
Tony Low Academic Affiliation: Department of Electrical & Computer Engineering, University of Minnesota, Minneapolis, US Talk: March 13, 2019 Manipulating light flow with 2D materials
Event Details
Tony Low
Academic Affiliation: Department of Electrical & Computer Engineering, University of Minnesota, Minneapolis, US
Talk: March 13, 2019
Manipulating light flow with 2D materials plasmons
Recent years have observed a plethora of strong dipole type polaritonic excitations in 2D materials owing to the reduced screening. These polaritons can be sustained as electromagnetic modes at the interface between a positive and negative permittivity material. In the case of the plasmon-polaritons (e.g. in semi-metallic graphene), the negative permittivity is provided by the coherent oscillations of the free carriers. For exciton-polaritons (e.g. in semiconducting transition metal dichalcogenides, TMD) and phonon-polaritons (e.g. in diatomic hexagonal boron nitride, hBN), it is associated with their resonant optical absorption, resulting from a highly dispersive permittivity. These optical resonances can also result in a negative permittivity, albeit over a narrow spectral window.
In this talk, I will discuss our recent efforts in understanding plasmons behavior in 2D materials and using them to control the flow of light both in the far- and near-field. The general constitutive materials response of 2D materials, in conjunction with metasurface approaches, can potentially enable arbitrary control of phase, amplitude, polarization of light. The flow of light within the 2D materials can also exhibit rich transport behavior, such as hyperbolic rays, non-reciprocal chiral propagation, time reversal of waves and coupling of light spin to induce one-way propagation.
Time
(Wednesday) 11:00 am - 12:00 am
february 2019
Event Details
Sebastian Loth Academic Affiliation: Institute for Functional Matter and Quantum Technologies, University of Stuttgart, Germany Talk: February 27, 2019 Ultrafast Charge-Density Wave Dynamics at
Event Details
Sebastian Loth
Academic Affiliation: Institute for Functional Matter and Quantum Technologies, University of Stuttgart, Germany
Talk: February 27, 2019
Ultrafast Charge-Density Wave Dynamics at the Atomic Scale
Combining the advantages of ultrafast laser spectroscopy and atomic-resolution scanning probe microscopy has been a dream for some time, which – owed to technological progress in reliable laser sources and picosecond electronics – has now become reality. I will discuss how focusing single-cycle Terahertz pulses into the junction of a scanning tunneling microscope enables spectroscopy of electron dynamics with atomic spatial and femtosecond temporal resolution.
We apply this new tool to study the dynamics of the charge-density wave (cdw) state in NbSe2 . We find that intense local THz excitation leads to a spatially heterogeneous response of the cdw at length scales down to 1 nm and relaxation times as fast as 600 fs. In particular, our local measurement reveals a low-energy excitation at 0.15 THz which we attribute to the previously hidden pinned phase mode excitation at individual atomic pinning sites. These measurements can be extended to a variety of low-dimensional correlated-electron materials and help us unravel the intricate connection between ultrafast dynamics and local fluctuations.
Time
(Wednesday) 10:00 am - 11:00 am
Event Details
Sebastian Loth Academic Affiliation: Institute for Functional Matter and Quantum Technologies, University of Stuttgart, Germany Talk: February 26, 2019 State-of-the-art in ultrafast scanning tunneling
Event Details
Sebastian Loth
Academic Affiliation: Institute for Functional Matter and Quantum Technologies, University of Stuttgart, Germany
Talk: February 26, 2019
State-of-the-art in ultrafast scanning tunneling microscopy
Combining the advantages of ultrafast laser spectroscopy and atomic-resolution scanning probe microscopy into one tool has been a dream for quite some time. Technological progress in picosecond electronics and reliable laser sources has now turned this dream into reality. Two methods appear particularly promising: all-electronic excitation and optical excitation by THz light.
All-electronic excitation offers a versatile platform in which radio frequency sources or arbitrary waveform generators can be used to study time domain dynamics such as spin relaxation or even frequency-domain information such as spin resonance. THz pump-probe spectroscopy, on the other hand, circumvents any bandwidth limits of cabling and directly excited the STM’s tunnel junction enabling time resolution of approximately 100 fs. Both techniques utilize the non-linearity of the tunneling current to down-convert the fast measurements into quasi-DC signals that are detectable in the STM. I will review recent progress of these techniques, the physics underlying the excitation and detection mechanism and applications to spins on surfaces.
Time
(Tuesday) 3:00 pm - 5:00 pm
Event Details
Ying Jiang Academic Affiliation: International Center for Quantum Materials, School of Physics, Peking University Talk: February 15, 2019 Peering into interfacial water by scanning
Event Details
Ying Jiang
Academic Affiliation: International Center for Quantum Materials, School of Physics, Peking University
Talk: February 15, 2019
Peering into interfacial water by scanning probe microscopy
Water at surfaces is ubiquitous in nature and plays an essential role in a broad spectrum of physics, chemistry, biology, energy and material sciences. One of the most fundamental issues is the characterization of H-bonding structure and related dynamics at molecular level. Ideally, attacking this problem requires the access to the internal degrees of freedom of water molecules, i.e. the directionality of OH bonds. However, it remains a great challenge due to the small mass and size of hydrogen. In this talk, I will present our recent progress on the development of scanning probe microscopy/spectroscopy (SPM/S) with ultrahigh sensitivity and resolution, and its application to surface water. I will first focus on how to achieve sub-molecular-resolution imaging (1,2) and single-bond vibrational spectroscopy of single water molecules (3). In the following, I will discuss the application of those techniques to water clusters, ion hydrates and two-dimensional ice layers on insulating and metal surfaces. Some important issues, including H-bonding topology (4), proton dynamics (5), nuclear quantum effects (3), ion transport (6), ice edge structure and growth, will be addressed. In the end, I will present an outlook on the future directions of water-solid interfaces as well as the challenges faced by this field.
Time
(Friday) 2:00 pm - 3:00 pm