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

TL;DR

This paper explores novel phase kink states in multi-band superconductors with broken time-reversal symmetry, revealing their stability, magnetic effects, and potential for creating topological excitations.

Contribution

It introduces new phase kink states in TRSB superconductors, analyzes their stability, and discusses their physical implications and potential for topological excitations.

Findings

Discovery of a new type of phase slip.

Spontaneous magnetic fields in kink regions.

Creation of topological excitations via local perturbations.

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. Main results are summarized as follows: (1) We find a new type of phase slip when the kink becomes unstable. (2) In the kink region, TRS is broken and spontaneous magnetic fields are induced. (3) In superconductors with TRSB, composite topological excitations associated with variations of both superconductivity phase and amplitude can be created by local perturbations, or due to proximity effect between normal metals.