Quantum Monte Carlo study of a two-species bosonic Hubbard model

Abstract

We consider a two-species hard-core boson Hubbard model for a supersolid, where two types of bosons represent vacancies and interstitials doped into a commensurate crystal. The on-site interspecies interaction can create bound states of vacancies and interstitials facilitating vacancy condensation at lower energies than in a single-species model, as suggested in an earlier mean-field study. Here, we carry out quantum Monte Carlo simulations to study possible supersolid phases of the model, which correspond to superfluid phases of the vacancies or interstitials. At low temperatures, we find three distinct superfluid phases. The extent of the phases and the nature of the phase transitions are discussed in comparison to mean-field theory. © 2008 The American Physical Society.