Superfluid Density in Conventional Superconductors: From Clean to Strongly Disordered

TL;DR

This paper reformulates the superfluid density expression in disordered superconductors, highlighting the limitations of the traditional dirty-limit approximation and emphasizing the need for more accurate theoretical-experimental comparisons across various disorder regimes.

Contribution

We present a new formulation of superfluid density that separates the dirty-limit term from additional contributions, improving analysis of experimental data in disordered superconductors.

Findings

The traditional dirty-limit term is insufficient for many experimental regimes.

A significant regime exists where theory and experiment must be carefully compared.

Our reformulation improves understanding of superfluid density across disorder levels.

Abstract

The highly convergent form of superfluid density in disordered conventional superconductors available in the literature and independently obtained by us following the approach of an earlier paper [Phys. Rev. B $\bm{102}$, 024514 (2020)] has been reformulated to separate out the generally used so-called `dirty-limit' term and an additional term. We use this new expression for making an extensive comparison with previously published experimental data and show that the former, generally used, term is {\em not} sufficient for analyzing these results. We point out that consequently, there is a large regime (disordered superconductors with moderate to no disorder) where theoretical predictions need to be confronted with experiment.