Currents induced by magnetic impurities in superconductors with spin-orbit coupling

TL;DR

This paper demonstrates that magnetic impurities in superconductors with spin-orbit coupling induce currents that depend on impurity properties, with significant effects near YSR state crossings, and these currents can be detected via spin-polarized measurements.

Contribution

It reveals the generation and characteristics of impurity-induced currents in spin-orbit coupled superconductors, linking them to YSR states and local spin polarization.

Findings

Currents depend strongly on magnetic moment orientation and magnitude.

Near YSR state zero-energy crossing, the current increases sharply.

Currents are orthogonal to local spin polarization and detectable via spin-polarized STM.

Abstract

We show that superconducting currents are generated around magnetic impurities and ferromagnetic islands proximity-coupled to superconductors with finite spin-orbit coupling. Using the Ginzburg-Landau theory, T-matrix calculation, as well as self-consistent numerical simulation on a lattice, we find a strong dependence of the current on the direction and magnitude of the magnetic moment. We establish that in the case of point magnetic impurities, the current is carried by the induced Yu-Shiba-Rusinov (YSR) subgap states. In the vicinity of the phase transition, where the YSR states cross at zero energy, the current increases dramatically. Furthermore, we show that the currents are orthogonal to the local spin polarization and, thus, can be probed by measuring the spin-polarized local density of states.