Pairing in disordered s-wave superconductors and the effect of their coupling

TL;DR

This study investigates how inhomogeneity and coupling affect s-wave superconductors, revealing that disorder suppresses superconductivity, proximity effects are strong, and coupled superconductors behave independently regardless of connector dimensions.

Contribution

It demonstrates that random local interactions suppress superconductivity and that coupled superconductors act independently, with the connector's size having negligible influence.

Findings

Disorder suppresses superconductivity compared to bimodal distributions.

Proximity effect causes all sites to develop non-zero pairing amplitude.

Coupling between superconductors has negligible impact regardless of connector size.

Abstract

Inhomogeneity is introduced through random local interactions (Ui) in an attractive Hubbard model on a square lattice and studied using mean-field Bogoliubov-de Gennes formalism. Superconductivity is found to get suppressed by the random Ui contrary to the results of a bimodal distribution of Ui. The proximity effect of superconductivity is found to be strong, all sites develop non-zero pairing amplitude. The gap in the density of states is always non-zero and does not vanish even for strong disorder. When two such superconductors are coupled via a channel, the effect of one on the other is negligible. The length and width of the connector, do not seem to have any noticeable effect on the superconductivity in either systems. The superconducting blocks behave as independent entity and the introduction of the channel have no effect on them.