Change of surface critical current in the surface superconductivity and mixed states of superconducting Niobium

TL;DR

This study investigates how different surface treatments affect the critical current in bulk Niobium, revealing significant changes in surface superconductivity and mixed states, with implications for superconducting surface properties.

Contribution

It provides a systematic analysis of how surface treatments influence the surface critical current and superconductivity states in Niobium, highlighting new phenomena in surface superconductivity behavior.

Findings

Critical current increases with surface abrasion up to a limit.

Surface superconductivity reaches critical current levels comparable to the mixed state.

Surface morphology influences nucleation of superconductivity in magnetic fields.

Abstract

A systematic study of irreversible magnetization was performed in bulk Niobium after different surface treatments. Starting with smooth surfaces and abrading them, a strong increase of the critical current is observed up an apparent limiting value. An impressive change of the critical current is also observed in the surface superconductivity (SSC) state, reaching values of the same order of magnitude as in the mixed state. We explain also the observation of strong SSC for magnetic field perpendicular to larges facets in terms of nucleation of SC along bumps of a corrugated surface.