Modification of the Magnetic Flux-Line Interaction at a Superconductor's Surface

TL;DR

This paper derives how magnetic flux lines interact near a superconductor's surface, revealing surface effects that modify their repulsive forces and elastic properties, especially relevant for anisotropic type-II superconductors.

Contribution

It introduces a detailed model of flux-line interactions at a superconductor surface, including stray field effects and surface contributions to elastic constants.

Findings

Stray fields near the surface add an exponentially decaying repulsive component.

Surface effects influence the elastic constants of flux-line arrays.

The model applies to anisotropic type-II superconductors in an external magnetic field.

Abstract

The pair interaction between magnetic flux lines in a semi-infinite slab of an anisotropic type-II superconductor in an external field is derived in the London limit. The case where the applied field is normal to the superconductor/vacuum interface is considered. The presence of stray fields near the surface leads to an additional contribution to the repulsive interaction between flux lines that vanishes exponentially with the distance from the interface. The pair interaction is used to obtain the continuum elastic energy of a distorted semi-infinite flux-line array. The presence of the superconductor/vacuum interface yields surface contributions to the compressional and tilt elastic constants.