Critical currents in soft type II superconductors

Abstract

A continuum description of the mixed state suggests that the critical state of soft superconductors is completely determined by the surface roughness. The disorder associated with surface irregularities gives rise to many non-dissipative states, including subcritical transport currents. The field and temperature dependence of critical currents is related to that of a local thermodynamic parameter, denoted as ε, which in turn is simply related to the ideal magnetization curve. This interpretation of critical currents and pinning is strongly supported by currently available experimental data.