Josephson Current between Triplet and Singlet Superconductors

TL;DR

This paper investigates the Josephson effect between triplet and singlet superconductors, revealing conditions for current flow influenced by spin-orbit coupling and analyzing experimental data with a non-unitary triplet state model.

Contribution

It provides a theoretical analysis of Josephson current conditions between triplet and singlet superconductors, including recent experimental observations.

Findings

Josephson current flows only when $L_z=-S_z=\pm 1$ in triplet superconductors.

Temperature and orientation dependence of critical current explained by non-unitary triplet state.

Theoretical conditions match experimental observations in UPt$_3$-Nb junctions.

Abstract

The Josephson effect between triplet and singlet superconductors is studied. Josephson current can flow between triplet and singlet superconductors due to the spin-orbit coupling in the spin-triplet superconductor but it is finite only when triplet superconductor has $L_z=-S_z=\pm 1$, where $L_z$ and $S_z$ are the perpendicular components of orbital angular momentum and spin angular momentum of the triplet Cooper pairs, respectively. The recently observed temperature and orientational dependence of the critical current through a Josephson junction between UPt$_3$ and Nb is investigated by considering a non-unitary triplet state.