Theory of the Josephson effect in superconductor / ferromagnet / superconductor junctions

TL;DR

This paper investigates how exchange interactions affect the Josephson current in superconductor/ferromagnet/superconductor junctions, revealing suppression in d-wave cases and enhancement when different symmetries are involved.

Contribution

It provides a theoretical analysis of the Josephson effect in unconventional superconductor/ferromagnet junctions, highlighting the role of symmetry and exchange interactions.

Findings

D-wave symmetry suppresses Josephson current with increased exchange interaction.

Different parity superconductors (s-wave and p-wave) show enhanced Josephson current due to exchange interactions.

Exchange interaction influences the Josephson effect differently depending on superconductor symmetry.

Abstract

To reveal the influence of the exchange interaction on the Josephson effect, the d.c. Josephson current in unconventional-superconductor / ferromagnet / unconventional-superconductor junctions is studied. When the two superconductors have d-wave symmetry, the Josephson current is drastically suppressed with the increase of the exchange interaction. On the other hand, when the two superconductors have different parities, e.g. s-wave and p-wave, an enhancement of the Josephson current is obtained with the increment of the exchange interaction due to the break-down of SU(2) symmetry in the spin space.