Dendritic flux avalanches and nonlocal electrodynamics in thin superconducting films

TL;DR

This paper investigates how nonlocal magnetic flux diffusion and thermomagnetic instabilities cause dendritic flux avalanches in thin superconducting films, combining numerical and analytical methods.

Contribution

It introduces a coupled nonlinear model explaining dendritic flux patterns and their dependence on defects, supported by experimental validation.

Findings

Branching of flux filaments due to nonlocal diffusion

Thermomagnetic edge instability triggers dendritic patterns

Distribution of avalanches depends on defect landscape

Abstract

We present numerical and analytical studies of coupled nonlinear Maxwell and thermal diffusion equations which describe nonisothermal dendritic flux penetration in superconducting films. We show that spontaneous branching of propagating flux filaments occurs due to nonlocal magnetic flux diffusion and positive feedback between flux motion and Joule heat generation. The branching is triggered by a thermomagnetic edge instability which causes stratification of the critical state. The resulting distribution of magnetic microavalanches depends on a spatial distribution of defects. Our results are in good agreement with experiments performed on Nb films.