Diode effect in Josephson junctions with a single magnetic atom
Martina Trahms, Larissa Melischek, Jacob F. Steiner, Bharti Mahendru, Idan Tamir, Nils Bogdanoff, O. Peters, Gaël Reecht, Clemens B. Winkelmann, Felix von Oppen, Katharina J. Franke
Abstract
Abstract Current flow in electronic devices can be asymmetric with bias direction, a phenomenon underlying the utility of diodes 1 and known as non-reciprocal charge transport 2 . The promise of dissipationless electronics has recently stimulated the quest for superconducting diodes, and non-reciprocal superconducting devices have been realized in various non-centrosymmetric systems 3–10 . Here we investigate the ultimate limits of miniaturization by creating atomic-scale Pb–Pb Josephson junctions in a scanning tunnelling microscope. Pristine junctions stabilized by a single Pb atom exhibit hysteretic behaviour, confirming the high quality of the junctions, but no asymmetry between the bias directions. Non-reciprocal supercurrents emerge when inserting a single magnetic atom into the junction, with the preferred direction depending on the atomic species. Aided by theoretical modelling, we trace the non-reciprocity to quasiparticle currents flowing by means of electron–hole asymmetric Yu–Shiba–Rusinov states inside the superconducting energy gap and identify a new mechanism for diode behaviour in Josephson junctions. Our results open new avenues for creating atomic-scale Josephson diodes and tuning their properties through single-atom manipulation.