Theory of disordered unconventional superconductors

TL;DR

This paper explores how disorder affects unconventional superconductors, revealing an intermediate s-wave superconducting phase emerging between the clean and metallic phases due to inhomogeneity and phase transitions.

Contribution

It introduces a theoretical framework describing the disorder-induced transition and the emergence of an intermediate s-wave phase in unconventional superconductors.

Findings

Disorder suppresses unconventional superconductivity leading to inhomogeneity.

An intermediate s-wave superconducting phase appears due to phase inhomogeneity.

The phase transition is described by the Mattis model of spin glasses.

Abstract

In contrast to conventional s-wave superconductivity, unconventional (e.g. p or d-wave) superconductivity is strongly suppressed even by relatively weak disorder. Upon approaching the superconductor-metal transition, the order parameter amplitude becomes increasingly inhomogeneous leading to effective granularity and a phase ordering transition described by the Mattis model of spin glasses. One consequence of this is that at low enough temperatures, between the clean unconventional superconducting and the diffusive metallic phases, there is necessarily an intermediate superconducting phase which exhibits s-wave symmetry on macroscopic scales.