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O: Fachverband Oberflächenphysik

O 28: Poster Session - Scanning Probe techniques: Method Development

O 28.10: Poster

Montag, 16. März 2020, 18:15–20:00, P1A

Single-atom electron paramagnetic resonance in a scanning tunneling microscope driven by a radiofrequency antenna at 4K
— •Stepan Kovarik, Tom S. Seifert, Corneliu Nistor, Luca Persichetti, Sebastian Stepanow, and Pietro Gambardella —
Department of Materials, ETH Zurich, Switzerland

Combining electron paramagnetic resonance (EPR) with scanning tunneling microscopy (STM) enables detailed insight into the interactions and magnetic properties of single atoms on surfaces [1]. A requirement for EPR-STM is the efficient coupling of microwave excitations to the tunnel junction. Here, we present a coupling efficiency of the order of unity by using a radiofrequency antenna placed parallel to the STM tip, which we interpret using a simple capacitive-coupling model [2]. We further demonstrate the possibility to perform EPR-STM routinely above 4 K using amplitude as well as frequency modulation of the radiofrequency excitation. We directly compare different acquisition modes on hydrogenated Ti atoms on bilayer MgO on Ag and highlight the advantages of frequency and magnetic field sweeps as well as amplitude and frequency modulation in order to maximize the EPR signal. The possibility to tune the microwave-excitation scheme and to perform EPR-STM at relatively high temperature and high power opens this technique to a broad range of experiments.
[1] S. Baumann et al., Science 350, 417 (2015)
[2] T. S. Seifert et al., arXiv:1908.03379 (2019)