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Description
Magnetic atoms on superconductors induce an exchange coupling, which leads to states within the superconducting energy gap. These so-called Yu-Shiba-Rusinov (YSR) states can be probed by scanning tunneling spectroscopy at the atomic scale. Here, we investigate single magnetic adatoms on a superconducting Pb surface.
As YSR states are within the superconducting energy gap, their excitation by electrons requires a subsequent inelastic relaxation process. At strong tunnel coupling, thermal relaxation is not sufficiently fast and resonant Andreev processes become the dominant tunneling process [1]. We obtain direct evidence of these two transport regimes by inserting GHz radiation into the STM junction and analyzing the photon-assisted tunneling maps [2,3].
[1] M. Ruby, F. Pientka, Y. Peng, F. von Oppen, B. W. Heinrich, K. J. Franke, Phys. Rev. Lett. 115, 087001 (2015).
[2] O. Peters, N. Bogdanoff, S. Acero Gonzalez, L. Melischek, J. R. Simon, G. Reecht, C. B. Winkelmann, F. von Oppen, K. J. Franke, Nature Physics 16, 1222 (2020).
[3] S. Acero Gonzalez, L. Melischek, O. Peters, K. Flensberg, K. J. Franke, F. von Oppen, Phys. Rev. B 102, 045413 (2020).
