Thermodynamic parameters of single- or multi-band superconductors derived from self-field critical currents

TL;DR

This paper demonstrates that the self-field critical current in superconductors universally relates to fundamental thermodynamic parameters, enabling extraction of these parameters across various materials without microstructural considerations.

Contribution

It generalizes the universal property of self-field critical current to diverse superconductor geometries and types, using extended BCS theory to accurately extract thermodynamic parameters from experimental data.

Findings

Self-field critical current is governed by the critical field and penetration depth.

Extracted parameters match well with known bulk values.

Multiband superconductors' individual contributions are accurately identified.

Abstract

Key questions for any superconductor include: what is its maximum dissipation-free electrical current (its `critical current') and can this be used to extract fundamental thermodynamic parameters? Present models focus on depinning of magnetic vortices and implicate materials engineering to maximise pinning performance. But recently we showed that the self-field critical current for thin films is a universal property, independent of microstructure, controlled only by the penetration depth. Here we generalise this observation to include thin films, wires or nanowires of single- or multi-band s-wave and d-wave superconductors. Using extended BCS theory we consider dissipation-free self-field transport currents as Meissner-London currents, avoiding the concept of pinning altogether. We find quite generally, for type I or type II superconductors, the current is limited by the relevant critical field divided by the penetration depth. Our fits to 62 available data sets, from zinc nanowires to compressed sulphur hydride with critical temperatures of 0.65 to 203 K, respectively, are excellent. Extracted London penetration depths, superconducting energy gaps and specific heat jumps agree well with reported bulk values. For multiband or multiphase samples we accurately recover individual band contributions and phase fractions.