Spontaneous spin accumulation in singlet-triplet Josephson junctions

TL;DR

This paper investigates how mismatched spin symmetries in singlet-triplet Josephson junctions lead to equilibrium spin accumulation, which can be detected by local magnetic probes and may identify triplet pairing in certain superconductors.

Contribution

It introduces the concept of equilibrium spin accumulation due to spin symmetry mismatch in singlet-triplet Josephson junctions and suggests experimental detection methods.

Findings

Spin imbalance causes net spin accumulation at the junction.

Detection possible via scanning SQUID, Hall, and Kerr probes.

Potential to identify triplet pairing in specific superconductors.

Abstract

We study the Andreev bound states in a Josephson junction between a singlet and a triplet superconductors. Because of the mismatch in the spin symmetries of pairing, the energies of the spin up and down quasiparticles are generally different. This results in imbalance of spin populations and net spin accumulation at the junction in equilibrium. This effect can be detected using probes of local magnetic field, such as the scanning SQUID, Hall, and Kerr probes. It may help to identify potential triplet pairing in $\rm(TMTSF)_2X$, $\rm Sr_2RuO_4$, and oxypnictides.