Ensemble Measurements of Spins on Surfaces


This team is pursuing a two-prong research agenda. Firstly, to follow the expertise of the PI to perform magnetic x-ray absorption studies at national and international synchrotron facilities around the world. Secondly, to develop a unique research tool, which will be able to measure ensemble-averaging electron spin resonance of atomic-scale quantum magnets on clean surfaces.

X-ray absorption (XAS) and magnetic circular dichroism (XMCD) are element specific techniques that offer unique sensitivity to extremely diluted amount of magnetic materials. We use these techniques to explore the magnetic properties of ensemble of atoms and molecules deposited on non-magnetic surfaces. Our focus is to investigate the stability of their magnetic states and the interactions determining the static and dynamic properties of their spin. We perform XAS and XMCD at several synchrotron facilities, partly in collaboration with other research teams. The PI was recently able to demonstrate that single Holmium atoms on thin layers of MgO have surprisingly long magnetic lifetime and exhibit magnetic remanence in hysteresis loop up to 40 K [Science 352, 318 (2016)]. Our current research in this area at QNS is trying to identify novel atomic-scale magnets that can preserve magnetic stability at ever-higher temperature.

Electron spin resonance (ESR) is a well-established technique for the study of quantum centers, such as color centers, in insulators. Nowadays it is also commonly applied in biology to help in structure determination of complex bio-molecules. We make use of this technique to explore the quantum coherence of atomic-scale magnets at the surface. We are currently developing a cryogenic ESR setup in collaboration with a research group at the Ecole Polytechnique Federale de Lausanne. This setup will operate in ultra-high vacuum conditions and will offer enhanced sensitivity to surface-supported magnetic systems, such as single atoms and single molecule magnets. With the results of these ensemble-averaging measurements, we will then perform STM based measurements on these systems. We believe that this approach will help significantly in the search for better quantum systems on surfaces.

Long-Term Goals

  • High-precision measurement on ensembles of atoms on surfaces
  • Develop fast screening ability for spins on surfaces

Near-Term Goals

  • Magnetic characterization of atoms and molecules on surfaces using X-ray absorption spectroscopy
  • Develop a surface-science, low-temperature electron spin resonance tool

Key Publications

F. Donati, S. Rusponi et al., Physical Review Letters (2020) ...
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Michał Studniarek, Christian Wäckerlin, et al., Advanced Science(2019) ...
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Iker Gallardo, Andres Arnau et al., New Journal of Physics 2019 ...
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Aparajita Singha, Fabio Donati et al., Physical Review Letters 2018 ...
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Romana Baltic, Fabio Donati et al., Physical Review B 2018 ...
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Fabian D. Natterer, Fabio Donati et al., Physical Review Letters 2018 ...
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Christian Wackerlin, Fabio Donati et al., The Journal of Physical Chemistry C 2018 ...
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Aparajita Singha, Romana Baltic et al., Physical Review B 2017 ...
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  • Fabio Donati
  • Denis Krylov
  • Luciano Colazzo
  • Franklin Cho
  • Safa Ahmed
  • Yejin Jeong
  • Jisoo Yu