Visitors

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.

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.

Date: September 25 – 27, 2019

Location: Center for Quantum Nanoscience at Ewha Womans University in Seoul, South Korea

Our Invited Speakers:

• Ali Yazdani – Physics Department of Princeton Univ. USA
• Andreas Heinrich – Director of IBS Center for Quantum Nanoscience, Korea
• Andrew Dzurak – School of Electrical Engineering and Telecommunications, UNSW, Australia
• Ania Jayich – Department of Physics, UCSB, USA
• Arzhang Ardavan – Department of Physics, Oxford Univ., UK
• Daniel Loss – Department of Physics, Univ. of Basel, Switzerland
• Donghun Lee – Physics Department of Korea Univ., Korea
• Fabio Donati – Center for QNS / Department of Physics at Ewha Univ. Korea
• Jelena Klinovaja – Department of Physics, Univ. of Basel, Switzerland
• Jiangfeng Du – ICQT and Department of Modern Physics, USTC Hefei, China
• Jörg Wrachtrup – Physics Department of University of Stuttgart, Germany
• Roberta Sessoli – Department of Chemistry, Univ. of Florence, Italy
• Taeyoung Choi – Center for QNS / Department of Physics at Ewha Univ., Korea
• Taner Esat – Center for QNS, Korea
• William D. Oliver – Department of Physics, Director at MIT Lincoln Lab, USA
• Wolfgang Wernsdorfer – Department of Physics, KIT Karlsruhe, Germany
• Yujeong Bae – Center for QNS, Korea

Visit https://icqns.org/ to learn more about our conference.