Broken time-reversal symmetry in Josephson junction involving two-band superconductors

TL;DR

This paper theoretically predicts a new time-reversal symmetry breaking state in Josephson junctions involving two-gap superconductors, caused by frustration among order parameters, leading to unique interface states with potential experimental signatures.

Contribution

It introduces a novel theoretical state with broken time-reversal symmetry in Josephson junctions involving two-gap superconductors, highlighting the role of frustration among order parameters.

Findings

Discovery of a time-reversal symmetry breaking state in the junction

Identification of interface states with energies inside the superconducting gap

Discussion of potential experimental observations

Abstract

A novel time-reversal symmetry breaking state is found theoretically in the Josephson junction between the two-gap superconductor and the conventional s-wave superconductor. This occurs due to the frustration between the three order parameters analogous to the two antiferromagnetically coupled XY-spins put under a magnetic field. This leads to the interface states with the energies inside the superconducting gap. Possible experimental observations of this state with broken time-reversal symmetry are discussed.