Voltage noise and surface current fluctuations in the superconducting surface sheath

TL;DR

This study measures voltage noise in surface superconductivity of a type-II superconductor, revealing surface vortex-induced current fluctuations that can be controlled by surface pinning, with implications for understanding surface noise.

Contribution

First measurement of voltage noise in surface superconductivity state, demonstrating surface vortex-induced current fluctuations and their dependence on surface pinning.

Findings

Surface vortices generate measurable voltage noise.

Surface current fluctuations can be modified by surface pinning.

Surface fluctuations explain noise even with bulk vortices present.

Abstract

We report the first measurements of the voltage noise in the surface superconductivity state of a type-II superconductor. We present strong evidences that surface vortices generates surface current fluctuations whose magnitude can be modified by the pinning ability of the surface. Simple two-stage mechanism governed by current conservation appears to describe the data. We conclude that large voltage fluctuations induced by surface vortices exist while the bulk is metallic. Furthermore, this experiment shows that sole surface current fluctuations can account for the noise observed even in the presence of vortices in the bulk.