Flux domes in superconducting films without edges

TL;DR

This paper predicts the formation of flux domes in superconducting films with bulk pinning, caused by vortex-antivortex pairs generated beneath current-carrying wires, expanding understanding beyond edge-related phenomena.

Contribution

It introduces a model for flux dome formation in films with bulk pinning due to vortex-antivortex pairs generated away from edges, under magnetic fields from external sources.

Findings

Flux domes occur in films with bulk pinning when vortices form away from edges.

Vortex-antivortex pairs are generated when magnetic field exceeds a critical value.

Magnetic field and current distributions are calculated for different pinning conditions.

Abstract

Domelike magnetic-flux-density distributions previously have been observed experimentally and analyzed theoretically in superconducting films with edges, such as in strips and thin plates. Such flux domes have been explained as arising from a combination of strong geometric barriers and weak bulk pinning. In this paper we predict that, even in films with bulk pinning, flux domes also occur when vortices and antivortices are produced far from the film edges underneath current-carrying wires, coils, or permanent magnets placed above the film. Vortex-antivortex pairs penetrating through the film are generated when the magnetic field parallel to the surface exceeds H_{c1}+K_c, where H_{c1} is the lower critical field and K_c = j_c d is the critical sheet-current density (the product of the bulk critical current density j_c and the film thickness d). The vortices and antivortices move in opposite directions to locations where they join others to create separated vortex and antivortex flux domes. We consider a simple arrangement of a pair of current-carrying wires carrying current I_0 in opposite directions and calculate the magnetic-field and current-density distributions as a function of I_0 both in the bulk-pinning-free case (K_c = 0) and in the presence of bulk pinning, characterized by a field-independent critical sheet-current density (K_c > 0).