Off equilibrium properties of vortex creep in superconductors

Abstract

We study a model for the dynamics of vortices in type II superconductors. In particular, we discuss glassy ``off equilibrium'' properties and ``aging'' in magnetic creep. At low temperatures a crossover point is found, Tg, where relaxation times seem to diverge a' la Vogel-Tamman-Fulcher. Magnetic creep changes by crossing Tg: above Tg power law creep is found asymptotically followed by stretched exponential saturation; below Tg the creep is logarithmic and vortex motion strongly subdiffusive. In this region violation of time translation invariance is found along with important dynamical scaling properties. A thermodynamic glassy transition point can be found at a lower temperature Tc.