SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 107: Poster Session VIII: Poster to Mini-Symposium: Manipulation and control of spins on functional surfaces IV
O 107.3: Poster
Donnerstag, 4. März 2021, 13:30–15:30, P
Supercurrent Reversal through Atomic Scale Yu-Shiba-Rusinov States — •Christian R. Ast1, Sujoy Karan1, Haonan Huang1, Ciprian Padurariu3, Björn Kubala3, Gonzalo Morrás2, Alfredo Levy Yeyati2, Juan Carlos Cuevas2, Joachim Ankerhold3, and Klaus Kern1,4 — 1MPI für Festkörperforschung, Stuttgart — 2Universidad Autónoma de Madrid, Spain — 3Universität Ulm — 4EPFL, Lausanne, Switzerland
Magnetic impurities on superconductors give rise to discrete bound states inside the superconducting gap known as Yu-Shiba-Rusinov (YSR) states. Varying the impurity-superconductor coupling induces a quantum phase transition (QPT) as the YSR state energy passes through zero. The concomitant sign change in the Josephson current – a long sought for hallmark of this QPT – has remained elusive so far. Using scanning tunneling microscopy (STM), we demonstrate such a 0 to π transition of a Josephson junction through a YSR state as we continuously change the impurity-superconductor coupling. We detect the sign change in the Josephson current by exploiting a second transport channel as a reference in analogy to a superconducting quantum interference device (SQUID), which provides a rudimentary phase sensitivity for the STM. The change in the Josephson current through the QPT is significant and demonstrates the role of the impurity spin as well as the parity change across the QPT.