Phase solitons in multi-band superconductors with and without time-reversal symmetry

Abstract

The Josephson-like interband couplings in multi-band superconductivity exhibit degenerate energy minima, which support states with kinks in phase of superconductivity. When the interband couplings in systems of three or more components are frustrated, the time-reversal symmetry (TRS) can be broken, which generates another type of phase kink between the two time-reversal symmetry breaking (TRSB) pair states. In this work, we focus on these novel states of phase kinks, and investigate their stability, similarity, differences and physical consequences. The main results can be summarized as follows: (i) we find a new type of phase slip when the kink becomes unstable. (ii) In the kink region, TRS is broken and spontaneous magnetic fields are induced. (iii) In superconductors with TRSB, composite topological excitations associated with variations of both the superconductivity phase and amplitude can be created by local perturbations or due to proximity effect between normal metals. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.