Mesoscopic gap fluctuations in an unconventional superconductor

TL;DR

This paper investigates how mesoscopic disorder causes spatial variations in the pairing temperature and gap in an unconventional superconductor, leading to a network of superconducting islands and metallic regions, with implications for high-temperature superconductors.

Contribution

It derives the probability distribution of pairing temperatures and gaps, revealing the role of mesoscopic fluctuations in unconventional superconductors and their relevance to experimental observations.

Findings

Disorder induces spatial variations in pairing temperature and gap.

Superconducting state forms a network of islands above the mean-field transition.

Gap fluctuations are linked to pairing temperature fluctuations in the pseudogap phase.

Abstract

We study mesoscopic disorder fluctuations in an anisotropic gap superconductor, which lead to the spatial variations of the local pairing temperature and formation of superconducting islands above the mean-field transition. We derive the probability distribution function of the pairing temperatures and superconducting gaps. It is shown that above the mean-field transition, a disordered BCS superconductor with an unusual pairing symmetry is described by a network of superconducting islands and metallic regions with a strongly suppressed density of states due to superconducting fluctuations. We argue that the phenomena associated with mesoscopic disorder fluctuations may also be relevant to the high-temperature superconductors, in particular, to recent STM experiments, where gap inhomogeneities have been explicitly observed. It is suggested that the gap fluctuations in the pseudogap phase should be directly related to the corresponding fluctuations of the pairing temperature.