GROUND-STATE PHASE-DIAGRAM OF AN INTERACTING BOSE MODEL WITH NEAR-NEIGHBOR REPULSION

We study the ground-state phase diagram of a one-dimensional lattice model of interacting bosons at commensurate filling. When the ratio of interaction strengths to bandwidth is small, the bosons condense into a superfluid phase. For large on-site repulsion, there is a phase transition to a localized Mott phase where the gap DELTA is nonzero and the Fourier transform at zero momentum of the density-density correlation function S(q = 0) diverges. For large intersite repulsion, S(q = pi) diverges first. By examining the superfluid density rho-s, in addition to the gap and S(q), we obtain a complete characterization of the phase diagram.