Equilibrium and off-equilibrium dynamics in a model for vortices in superconductors

Abstract

We study a model for the dynamics of vortices in type-II superconductors. In particular, we discuss the magnetization relaxation close to and off equilibrium. At low temperatures a crossover point is found, ${T}_{g},$ where relaxation times become huge and seem to diverge according a Vogel-Tamman-Fulcher law at a lower temperature ${T}_{c}$ where a thermodynamic glass transition might be located. Magnetic creep changes by crossing ${T}_{g}:$ below ${T}_{g},$ vortex motion is strongly subdiffusive and logarithmic creep is found; above ${T}_{g},$ a power-law creep is asymptotically followed by stretched exponential saturation. The analysis of the self-scattering function also reveals that the dynamical process is non-Gaussian. In the regime below ${T}_{g},$ strong ``memory'' and ``aging'' effects appear. In particular, we analyze the properties of ``aging'' and the structure of its ``dynamical scaling.''