PATH-INTEGRAL MONTE-CARLO SIMULATION OF VORTICES

One of the most fascinating properties of high-T-c superconductors is the existence of a thermodynamic phase-transition located well below t he mean field transition line H-c2. This transition is a first order m elting transition of the Abrikosov vortex lattice into a entangled vor tex liquid, and is signalled by a discontinuity in the magnetization. On the London level, the vortex system can be mapped onto interacting bosons in two dimensions. We use this mapping to simulate the vortex s ystem with Path Integral Monte Carlo methods. This approach does not i ntroduce an underlying lattice and allows for the simultaneous investi gation of crystalline and longitudinal long-range order. We find a fir st-order transition as the system passes from a lattice to an entangle d liquid. The jump in the magnetization is in agreement with experimen ts. The phase diagrams of bosons and of vortices are discussed.