Andreev spectrum of a Josephson junction with spin-split superconductors

TL;DR

This paper investigates how intrinsic exchange fields in spin-split superconductors affect Andreev bound states and charge transport in Josephson junctions, revealing configurations with spin-split states and phase-dependent supercurrent behaviors.

Contribution

It provides a theoretical analysis of Andreev spectra in Josephson junctions with spin-split superconductors, highlighting the impact of exchange field orientation on bound states and supercurrent mechanisms.

Findings

Parallel exchange fields produce spin-split Andreev states.

Antiparallel exchange fields eliminate spin-splitting and bound states at small phase differences.

Supercurrent can be carried by bound states or continuous spectrum depending on configuration.

Abstract

The Andreev bound states and charge transport in a Josephson junction between two superconductors with intrinsic exchange fields are studied. We find that for a parallel configuration of the exchange fields in the superconductors the discrete spectrum consists of two pairs of spin-split states. The Josephson current in this case is mainly carried by bound states. In contrast, for the antiparallel configuration we find that there is no spin-splitting of the bound states and that for phase differences smaller than certain critical value there are no bound states at all. Hence the supercurrent is only carried by states in the continuous part of the spectrum. Our predictions can be tested by performing a tunneling spectroscopy of a weak link between two spin-split superconductors.