Diode effect in Josephson junctions with a single magnetic atom

TL;DR

This study demonstrates the creation of atomic-scale Josephson diodes by inserting a single magnetic atom into Pb--Pb junctions, revealing non-reciprocal supercurrents driven by Yu-Shiba-Rusinov states, advancing miniaturized superconducting diode technology.

Contribution

The paper introduces a method to induce and control non-reciprocal supercurrents in atomic-scale Josephson junctions using single magnetic atoms, supported by theoretical modeling.

Findings

Non-reciprocal supercurrents appear with magnetic atoms in the junction.

The direction of non-reciprocity depends on the atomic species.

Yu-Shiba-Rusinov states mediate the non-reciprocal current.

Abstract

Current flow in electronic devices can be asymmetric with bias direction, a phenomenon underlying the utility of diodes and known as non-reciprocal charge transport. 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. Probing the ultimate limits of miniaturization, we have created atomic-scale Pb--Pb Josephson junctions in a scanning tunneling microscope. Pristine junctions stabilized by a single Pb atom exhibit hysteretic behavior, 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 via Yu-Shiba-Rusinov (YSR) states inside the superconducting energy gap. Our results open new avenues for creating atomic-scale Josephson diodes and tuning their properties through single-atom manipulation.