Numerical Study on the Vortex States of High-T_(c) Superconductors with Point Defects: Novel Phases in the Vortex Liquid Region

摘要

Phase diagram of high-T_(c) vortex states in B ‖ c with point defects is investigated by large-scale Monte Carlo simulations. We find that the first-order boundary between the vortex slush and vortex liquid phases terminates at a critical point, and that there is a step of the specific heat above the critical point as reported experimentally. As the system size increases, this step becomes sharper but smaller, and is associated with a crossover rather than a thermodynamic phase transition.