Velocity-fluctuations–dominated flux-flow noise in the peak effect

Strong excess flux-flow voltage noise commonly observed in the vicinity of the peak effect in superconductors has recently been ascribed to a novel unconventional noise mechanism. The mechanism consists in random injection of the strongly pinned metastable disordered vortex phase through the sample edges and its subsequent random annealing into the weakly pinned ordered phase in the bulk. This results in large critical-current fluctuations causing strong vortex velocity fluctuations. In this paper we present the evidence that flux-flow noise in the peak effect regime is dominated by vortex velocity fluctuations while density fluctuations, considered in the conventional flux-flow noise models, are negligibly weak