A general interpolation scheme for thermal fluctuations in superconductors

TL;DR

This paper introduces a versatile interpolation method for modeling thermal fluctuations in superconductors, extending the Ginzburg-Landau theory with a gauge-invariant approach that aligns well with experimental data.

Contribution

It develops a general variational interpolation scheme for thermal fluctuations in superconductors, improving upon mean field models with broad applicability.

Findings

Correlation and penetration lengths deviate from mean field predictions.

The method accurately fits experimental data across various materials.

The approach is gauge-invariant and variational, ensuring physical consistency.

Abstract

We present a general interpolation theory for the phenomenological effects of thermal fluctuations in superconductors. Fluctuations are described by a simple gauge invariant extension of the gaussian effective potential for the Ginzburg-Landau static model. The approach is shown to be a genuine variational method, and to be stationary for infinitesimal gauge variations around the Landau gauge. Correlation and penetration lengths are shown to depart from the mean field behaviour in a more or less wide range of temperature below the critical regime, depending on the class of material considered. The method is quite general and yields a very good interpolation of the experimental data for very different materials.