Inversion mechanism for the transport current in type-II superconductors

TL;DR

This paper presents a theoretical analysis of the inversion of transport current in type-II superconductors, revealing conditions under which current flow reverses and exhibits paramagnetic behavior due to flux dynamics.

Contribution

It introduces a new theoretical framework combining analytical and numerical methods to predict current inversion and related phenomena in type-II superconductors.

Findings

Current inversion occurs under certain experimental conditions.

Inhomogeneous current density profiles with negative peripheral values are predicted.

Paramagnetic behavior can emerge locally and globally in the material.

Abstract

The longitudinal transport problem (the current is applied parallel to some bias magnetic field) in type-II superconductors is analyzed theoretically. Based on analytical results for simplified configurations, and relying on numerical studies for general scenarios, it is shown that a remarkable inversion of the current flow in a surface layer may be predicted under a wide set of experimental conditions. Strongly inhomogeneous current density profiles, characterized by enhanced transport toward the center and reduced, or even negative, values at the periphery of the conductor, are expected when the physical mechanisms of flux depinning and consumption (via line cutting) are recalled. A number of striking collateral effects, such as local and global paramagnetic behavior, are predicted. Our geometrical description of the macroscopic material laws allows a pictorial interpretation of the physical phenomena underlying the transport backflow.