Flux exchange in inhomogeneous type-II superconductors

TL;DR

This paper investigates magnetic flux exchange between different pinning regions in inhomogeneous type-II superconductors, revealing how it affects internal magnetic fields and depends on the superconductor's size.

Contribution

It introduces a differential equation model for flux exchange in inhomogeneous superconductors and analyzes its effects on internal magnetic fields.

Findings

Flux exchange reduces the internal field in weak pinning regions.

Flux exchange increases the internal field in strong pinning regions.

The flux exchange phenomenon is significantly influenced by the superconductor's size.

Abstract

The vortex hopping motion in a type-II superconductor determines the current-carrying ability and consequently the application fields of the superconductor. However, it is not clear how the vortices hop between the different pinning regions in the superconductor. Here we proposed that there should be magnetic \textit{flux exchange} between two contacting pinning regions. A system of differential equations was constructed to describe the flux exchange phenomenon. The qualitative analysis methods were used. The approximate numerical solutions and approximate analytical solutions of the system were obtained. The results show that the flux exchange reduces the internal field in a weak pinning region, but increases the internal field in a strong pinning region. Moreover, the flux exchange phenomenon is strongly influenced by the superconductor's geometrical size.