Katharina J. Franke Affiliation: Freie Universität Berlin Research Field: Scanning Tunneling Microscopy of magnetic adatoms on superconductors, Molecules on surfaces Talk: August 21, 11:00
Katharina J. Franke
Affiliation: Freie Universität Berlin
Research Field: Scanning Tunneling Microscopy of magnetic adatoms on superconductors, Molecules on surfaces
Talk: August 21, 11:00 -12:00
Transport properties through Shiba states
Magnetic adsorbates on conventional s-wave superconductors lead to exchange interactions that can induce bound states inside the superconducting energy gap. These states are known as YuShiba-Rusinov states (or Shiba states) and can be resolved by scanning tunneling spectroscopy as a pair of resonances at positive and negative bias voltages in the superconducting gap. Here, we employ tunneling spectroscopy at 1.1 K to investigate magnetic atoms on a superconducting Pb surface. The single-atom junctions are stable over several orders of magnitude in conductance. We observe two different transport regimes: at large tip-sample distance, the tunneling current is dominated by single-electron processes. However, these require the relaxation of electrons/holes from the Shiba states into the superconductor. At small tip-sample distance, the relaxation processes are not sufficiently fast for an efficient depopulation of the states, and thus Andreev processes become important, which resonantly transfer a Cooper pair into the superconductor. We probe the nature of the two-electron transport processes by irradiating the junction with microwaves from an antenna placed close to the junction. The tunneling electrons absorb or emit photons from the microwave field resulting in a distinct pattern of split Shiba states as a function of irradiation power.
(Wednesday) 11:00 am - 12:00 pm