First-order phase transition in a three-dimensional vortex system: Modeling Bi2Sr2CaCu2O8 in high magnetic fields

The nature of the vortex matter and its phase transitions in high-temperature superconducting oxides still present open issues, although results from a number of experiments and theoretical studies do support first-order transitions both at low and high applied magnetic fields. We report on first-order melting transitions obtained via Monte Carlo simulations using the Lawrence-Doniach (LD) model for vortices in strongly anisotropic layered superconductors, focusing on a clean three-dimensional sample of ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8}$, with dc magnetic field perpendicular to the ${\mathrm{CuO}}_{2}$ superconducting planes. In particular, our investigations indicate that in the high-field regime the ${\mathrm{CuO}}_{2}$ planes decouple at the melting transition, in agreement with very recent experimental observations. Moreover, contrary to some theoretical suggestions, we confirm Nelson's predictions for the random-walk-like diffusion of the melted lines along the direction of the applied field. Our results extend and clarify previous studies using the LD model and suggest the reliability of this framework in describing strongly anisotropic layered superconductors.