Voltage noise and surface current fluctuations in the superconducting surface sheath

We report the first measurements of the voltage noise in the surface superconductivity state of a type-II superconductor. We present strong evidence that surface vortices generate surface current fluctuations whose magnitude can be modified by the pinning ability of the surface. The 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.