Condensation transition in the one-dimensional extended Hubbard model

We study the phase diagram of the one-dimensional extended Hubbard model in the half-filled-band sector for an attractive nearest-neighbor interaction V. A first-order condensation transition occurs at a critical value of V which is a function of the on-site repulsion U. We obtain the phase boundary in strong coupling for U{→}{∞} and U{→}-{∞}, and, from a variational estimate, for U=0. We then compute the phase boundary numerically using a Monte Carlo simulation technique. Our numerical estimates join smoothly the strong-coupling regimes for {}U{}{~}4, and agree with the variational estimate at U=0 within 10%.