Simulated phase diagram of high- Tc vortex systems with point pins

Abstract

In order to study effects of point pins in high- T c vortex systems, randomly-distributed plaquettes with weak interactions are introduced to the three-dimensional frustrated XY model. Simulated results are consistent with theoretical predictions and experiments. That is, the first-order flux-line melting transition occurs in small density of point pins (the vortex liquid-Bragg glass transition), and the second-order glass transition takes place in large density of point pins (the vortex liquid-vortex glass transition). In the Bragg glass phase, the structure factor shows a triangular Bragg pattern and the percentage of entangled flux lines is very small, while these quantities in the vortex glass phase are not different from those in the vortex liquid phase.