Quantitative analysis of the critical current due to vortex pinning by surface corrugation

TL;DR

This study quantitatively analyzes how surface roughness affects vortex pinning and critical current in Nb films, demonstrating that increased roughness enhances vortex pinning and critical current through boundary condition effects.

Contribution

It provides a quantitative framework linking surface roughness spectral properties to vortex pinning and critical current in superconducting films.

Findings

Surface roughness increases critical current.

Spectral analysis explains boundary pinning effects.

Focused Ion Beam roughening enhances vortex pinning.

Abstract

The transport critical current of a Niobium (Nb) thick film has been measured for a large range of magnetic field. Its value and variation are quantitatively described in the framework of the pinning of vortices due to boundary conditions at the rough surface, with a contact angle well explained by the spectral analysis of the surface roughness. Increasing the surface roughness using a Focused Ion Beam results also in an increase of the superficial critical current.