Transport and vortex pinning in micron-size superconducting Nb films

Abstract

We have carried out Hall measurements on thin films of Nb in the flux-flow regime. The Hall bars were several microns in scale. Oscillations with magnetic field in the transverse and longitudinal resistances between the depinning field Bd and the upper critical field Bc2 are observed below Tc. The Hall effect may even change sign. The transverse and longitudinal resistances are interpreted in terms of current-driven motion of vortices in the presence of a few impurities. Simulations from time-dependent Ginzburg-Landau equations confirm this argument. © 2004 The American Physical Society.