Relaxation and a non-local, resistivity boundary layer in superconductors

TL;DR

This paper uses numerical simulations to explore how superconductors relax from thermal excitations, revealing a non-local resistivity boundary layer near the critical temperature that explains resistance behavior.

Contribution

It introduces a microscopic stability model and continuum simulations to explain resistance curvature and boundary layers in superconductors near critical temperature.

Findings

Identification of a non-local resistivity boundary layer near T_Crit.

Explanation of resistance curvature below T_Crit.

Alternative interpretation of increased conductivity above T_Crit.

Abstract

Superconductors like other solids cannot relax instantaneously from thermally excited (disturbed) states to thermodynamic equilibrium. In this paper, relaxation of a multi-filamentary and of a thin film superconductor from thermal excitations is simulated. Absorption of radiation or, under conductor movement, release and transformation of mechanical tension to thermal energy are examples. The paper applies numerical simulations of superconductor energy states, as many-particle systems, under basic thermodynamic and standard, multi-component heat transfer principles (solid conduction plus radiation in thin films). A recently described microscopic stability model and application of a traditional, continuum cell model allows to explain curvature of the resistance vs. temperature excursion below critical temperature, TCrit, and suggests an alternative to standard explanation of increased electrical conductivity at temperature exceeding TCrit. A non-local, resistivity boundary layer (a temperature uncertainty) is observed near critical temperature within which the resistivity curve smoothly approaches, from the superconducting state, the normal conduction resistivity. Keywords Superconductor; phase transition; relaxation; critical current density; critical temperature; thermal fluctuations; boundary layers