Vortices and 2D Bosons: A Path-Integral Monte Carlo Study

The vortex system in a high-Tc superconductor has been studied numerically using the mapping to 2D bosons and the Path Integral Monte Carlo method. We find a single first-order transition from an Abrikosov lattice to an entangled vortex liquid. The transition is characterized by an entropy jump of ∆S ≈ 0.27kB per degree of freedom and a Lindemann number cL ≈ 0.29. At low fields, λ ≈ a0, the density is reduced by ∆ρ/ρ ≈ 0.0003 upon melting. The vortex liquid corresponds to a bosonic superfluid, with ρs = ρ even in