Ground-state parameters, finite-size sealing, and low-temperature properties of the two-dimensional S=1/2 XY model

We present high-precision quantum Monte Carlo results for the S=1/2 XY mode l on a two-dimensional square lattice, in the ground stare as well as at fi nite temperature. The energy, the spin stiffness, the magnetization, and th e susceptibility are calculated and extrapolated to the thermodynamic limit . For the ground state, we test a variety of finite-size scaling prediction s of effective Lagrangian theory and find good agreement and consistency be tween the finite-size corrections for different quantities. The low-tempera ture behavior of the susceptibility and the internal energy is also in good agreement with theoretical predictions. [S0163-1829(99)06733-8].