Virtual Workshop on Scanning Probe Microscopy
Thursday, June 18th, 2020
9:00 - 13:00 CEST (view in your time zone)
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, he event has been a great opportunity to discuss the latest advances and keep sharing results despite the current lack of in-person conferences. We thank the 250 attendees and 28 poster presenters, and our 3 wonderful speakers for making this meeting a success!
9:10 Taeyoung Choi , Ewha Womans University and IBS Center for Quantum Nanoscience, Seoul (South Korea)
Electron spin resonance on individual atoms and molecules on surfaces
Xue Zhang, Yu Wang, Philip Willke, Aparajita Singa, Minhee Choi, Taeyoug Choi
Scanning tunneling microscopy (STM) studies of spin properties arising from individual atoms and nanostructures on surfaces have demonstrated nanoscale memory bits and logic gates toward miniaturizing electronic and information devices. In recent years, understanding and controlling individual spins with maintaining quantum coherence become one of highly interesting research topics to utilize the coherent spins for quantum sensing and information processing. Recently, we successfully combined a conventional electron spin resonance (ESR) technique with a spin-polarized STM and coherently drive spins of individual Fe and Ti atoms on ultrathin insulating MgO. Using this newly developed ESR-STM, we studied magnetic interaction of individual atoms that are coupled through magnetic dipolar and exchange interactions. Unique and advantageous aspects of ESR-STM compared to other quantum magnetic sensors (such as NV centers) are the atom manipulation and imaging capabilities, which allow us to build atomically precise nanostructures and examine their interactions. In addition, we found that both a spin-polarized tip and an external magnetic field play important role to drive the single-atom ESR. Utilizing stronger interaction between a spin-polarized tip and an atom on surface, we successfully drive the single-atom ESR without any external magnetic field which may be useful to study spin systems under low magnetic fields. Lastly, we use the ESR-STM technique to investigate single atom-molecule complexes as well as Dy (4f elements) atoms to investigate spin distribution across the complexes and to lengthen the coherence time of the spins. Coherent quantum control of individual atoms on surfaces combined with atom manipulation may promise the STM as a new and unique platform for a quantum sensor, investigating spin-labeled molecular structures and a quantum information processor, modeling quantum magnetism.
9:55 Katharina Franke, FU Berlin (Germany)
Scanning tunneling spectroscopy of organic molecules on single-layer MoS2 on Au(111)
Nils Krane, Gaël Reecht, Christian Lotze, Katharina Franke
Adsorption of organic molecules on metal surfaces typically leads to strong hybridization of the frontier molecular orbitals with the substrate electronic bands. This results in broad energy levels reflecting the ultrashort lifetime of excited molecular states in tunneling experiments. A monolayer of MoS2 is direct-bandgap semiconductor. Here, we show that single-layer MoS2 on Au(111) acts as an efficient decoupling layer for organic molecules. The decoupling efficiency is superior to frequently employed ionic layers such as NaCl, or to graphene. Molecular resonances within the semiconducting band gap of MoS2 exhibit widths of only a few meV. This exquisite energy resolution allows to study vibrational excitations within the individual molecules. Details in the set of vibronic resonances on thienothiophene-based molecules allow for their rotamer identification. The spatial intensity distribution along the molecule further reveals that the simple Franck-Condon picture is insufficient for a complete understanding of the excitation mechanism.
10:40 Jascha Repp, University of Regensburg (Germany)
Tunneling microscopy on insulators provides access to out-of-equilibrium charge states
Laerte L. Patera, Fabian Queck, Philipp Scheuerer, Jascha Repp
Scanning Tunneling Microscopy (STM) is a powerful tool for the investigation of individual molecules, being able to probe their orbitals with sub-molecular resolution. However, the requirement of a conductive substrate strongly limits the accessible electronic transitions. Conversely, atomic force microscopy (AFM) can be extended to insulating substrates, providing structural and electrostatic information. However, electronic states are generally not accessible by AFM. Here we exploit the single-electron sensitivity of AFM  in detecting electrostatic forces to establish a novel mode in scanning probe, in which an alternating current instead of a direct current probes the sample. Only a single electron per AFM-cantilever oscillation cycle tunnels between tip and investigated structure back and forth, enabling operation in absence of any conductance of the underlying substrate but still capable of imaging electronic states with Angstrom resolution. Our results unveil the effects of electron-transfer and polaron formation on the single-orbital scale .
 J. Klein, C. C. Williams, Appl. Phys. Lett. 79, 1828 (2001);
 L. L. Patera et al., Nature 566, 245 (2019).
11:25 - 11:45 Break
11:45 Poster session
Format - Each poster presenter will have their own Zoom link leading to the discussion room for their poster - Poster presenters are encouraged to send a 1-min video briefly explaining the content of their poster. The videos will be available outside of the discussion rooms for attendees to see, so that the Zoom conversation can be focused on questions - The poster session will be divided in two 40-min parts to ensure all presenters will also have the opportunity to look at posters
Guidelines for poster preparation - Keep your poster simple, so people can look at it easily on their screen. Use a horizontal format (5MB max size). - Make a short video (1 min) to present the your poster (recommended). - Create your Zoom link. Don't share it on social media to avoid zoombombing: the organizers will send make the links available to all participants.
Poster abstracts can be viewed here.
Fabio Donati, Ewha Womans University, Seoul, South Korea
Fabian Natterer, University of Zurich, Switzerland
Giulia Pacchioni, Nature Reviews Materials, London, UK
Marina Pivetta, EPFL, Lausanne, Switzerland
Aparajita Singha, Max Planck Institute for solid state research, Stuttgart, Germany