Unified Phase Diagram for the Three-Dimensional XY Model of a Point Disordered Type-II Superconductor

Abstract

We carry out extensive Monte Carlo simulations of the three-dimensional (3D) uniformly frustrated XY model with uncorrelated randomly perturbed couplings, as a model for the equilibrium behavior of an extreme type-II superconductor with quenched uncorrelated random point vortex pinning, in the presence of a uniform applied magnetic field. We map out the resulting phase diagram as a function of temperature T and pinning strength p for a fixed value of the vortex line density. At low p we find a sharp first order vortex lattice melting phase boundary separating a vortex lattice from a vortex liquid. As p increases, it appears that this first order transition smears out over a finite temperature interval, due to the effects of the random pinning, in agreement with several recent experiments. At large p we find a second order transition from vortex liquid to vortex glass.