Initial dissipation and current-voltage characteristics of superconductors containing fractal clusters of a normal phase

Abstract

The influence of fractal clusters of a normal phase on distinctive features of current-voltage characteristic of percolative type-II superconductors is considered. The results of high-resolution measurements of the differential resistance of BPSCCO/Ag composites are discussed in the context of magnetic flux dynamics. The region of initial dissipation is observed on current-voltage characteristics in the neighborhood of the transition into a resistive state. In the course of this stage of resistive transition the vortices start to break away from the normal-phase clusters, which act as pinning centers. The effect of transport current on vortex depinning is investigated. A broad current range of initial dissipation is considered as an evidence of fractal nature of the normal-phase clusters.