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

Abstract

A novel time-reversal symmetry breaking state is found theoretically in the Josephson junction between a two-gap superconductor and a conventional s-wave superconductor. This occurs as a result of frustration between the three order parameters analogous to two antiferromagnetically coupled XY-spins put under a magnetic field. This leads to formation of interface states with energies inside the superconducting gap and modified flux quantization condition for a ring composed of the two types of superconductors.