Superfluid to normal phase transition in strongly correlated bosons in two dimensions

Using quantum Monte Carlo simulations, we investigate the finite-temperature phase diagram of hard-core bosons (XY model) in two-dimensional lattices. To determine the phase boundaries, we perform a finite-size-scaling analysis of the superfluid stiffness in two different ways and find that both approaches provide results of comparable accuracy. Furthermore, we discuss how such a phase diagram can be determined by measuring the occupancy of the zero momentum mode in homogeneous and trapped systems. The latter approach can be used in current experiments with ultracold gases.