Flux penetration in slab shaped Type-I superconductors

TL;DR

This paper investigates how magnetic flux penetrates slab-shaped Type-I superconductors, revealing an instability that causes flux to invade in bursts and form complex structures, contrasting with gradual penetration.

Contribution

It introduces a model showing flux penetration occurs via bursts and droplet formation, highlighting an instability not previously characterized in such superconductors.

Findings

Flux penetrates via bursts rather than gradually.

Formation of isolated normal phase droplets during flux invasion.

Flux domain structure resembles experimental observations.

Abstract

We study the problem of flux penetration into type--I superconductors with high demagnetization factor (slab geometry).Assuming that the interface between the normal and superconducting regions is sharp, that flux diffuses rapidly in the normal regions, and that thermal effects are negligible, we analyze the process by which flux invades the sample as the applied field is increased slowly from zero.We find that flux does not penetrate gradually.Rather there is an instability in the process and the flux penetrates from the boundary in a series of bursts, accompanied by the formation of isolated droplets of the normal phase, leading to a multiply connected flux domain structure similar to that seen in experiments.