Phase Transitions in a Hard-Core Boson Model in Two Dimensions

Abstract

We study quantum phase transitions of a hard-core boson model with nearest-neighbor repulsion in two dimensions. By tuning chemical potential at a fixed hopping strength, the system undergoes a phase transition from solid phase to superfluid phase. Via quantum Monte Carlo with directed loop algorithm, we find that there is hysteresis in density of bosons as a function of chemical potential. This result is reinforced by the analysis of the histogram of density near the transition, where we obtain two peaks. Our result confirms that the transition is of the first order and we find no sign of a macroscopic supersolid state.