Time-Reversal-Symmetry-Broken Superconductivity Induced by Frustrated Inter-Component Couplings

TL;DR

This paper introduces a new type of superconductivity where time-reversal symmetry is broken without internal magnetic fields, driven by frustrated inter-component couplings, with implications for experimental verification and classification.

Contribution

It derives stability conditions for this novel TRSB superconductivity using Ginzburg-Landau theory and explores its unique properties and experimental signatures.

Findings

Multiple divergent coherence lengths identified

Superconductivity cannot be classified as type I or II by GL number

Critical Josephson current is suppressed between different chiralities

Abstract

Superconductivity is associated with spontaneously broken gauge symmetry. In some exotic superconductors the time-reversal symmetry is broken as well, accompanied with internal magnetic field. A time-reversal symmetry broken (TRSB) superconductivity without internal magnetic field involved can be induced by frustrated inter-component couplings, which becomes a realistic issue recently due to the discovery of iron-pnictide superconductors. Here we derive stability condition for this novel TRSB state using the Ginzburg-Landau (GL) theory. We find that there are multiple divergent coherence lengths, and that this novel superconductivity cannot be categorized by the GL number into type I or type II. We reveal that the critical Josephson current of a constriction junction between two bulk superconductors of different chiralities is suppressed significantly from that for same chirality. This effect provides a unique way to verify experimentally this brand new superconductivity.