Gapless Time-Reversal Symmetry Breaking Superconductivity

TL;DR

This paper explores a layered superconductor with a sign-changing order parameter, revealing conditions for gapless superconductivity and explaining surface-specific time-reversal symmetry breaking observed in experiments.

Contribution

It introduces a model of layered superconductors with phase-sign switching, linking it to gapless states and surface-specific symmetry breaking phenomena.

Findings

Gapless superconductivity occurs at high interlayer coupling.

Surface signals of time-reversal symmetry breaking are explained.

Model aligns with experimental observations in high-temperature superconductors.

Abstract

We consider a layered superconductor with a complex order parameter whose phase switches sign from one layer to the next. This system is shown to exhibit gapless superconductivity for sufficiently large interlayer pairing or interlayer hopping. In addition, this description is consistent with experiments finding signals of time-reversal symmetry breaking in high-temperature superconductors only at the surface and not in the sample bulk.