Vortex pinning by large normal particles in high-Tcsuperconductors

Abstract

We present a model of flux pinning on large nonsuperconducting particles. It is assumed that the pins trap different numbers of vortices determined by the Poisson's distribution function. This approach brings an additional factor into the expression for pinning force density that exponentially decays with field. The critical current density thus becomes at low fields nearly pure exponential function of magnetic field, in agreement with numerous experiments on high-${T}_{c}$ superconductors.