2-DIMENSIONAL SUPERFLUIDITY AND LOCALIZATION IN THE HARD-CORE BOSON MODEL - A QUANTUM MONTE-CARLO STUDY

Quantum Monte Carlo simulations are used to investigate the two-dimens ional superfluid properties of the hard-core boson model, which show a strong dependence on particle density and disorder. We obtain further evidence that a half-filled clean system becomes superfluid via a fin ite-temperature Kosterlitz-Thouless transition. The relationship betwe en low-temperature superfluid density and particle density is symmetri c and appears parabolic about the half-filling point. Disorder appears to break the superfluid phase up into two distinct localized states, depending on the particle density. We find that these results strongly correlate with the results of several experiments on high-T(c) superc onductors.