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

TL;DR

This study uses Monte Carlo simulations to explore the phase diagram of a 3D XY model representing a disordered type-II superconductor, revealing a transition from vortex lattice to vortex liquid and then to vortex glass as disorder increases.

Contribution

It provides a comprehensive phase diagram for a disordered superconductor model, highlighting the effects of random pinning on vortex phase transitions.

Findings

First order vortex lattice melting at low disorder

Transition smears with increasing disorder

Second order vortex liquid to vortex glass transition at high disorder

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.