Condensation transition in the one-dimensional extended Hubbard model.

Abstract

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\ensuremath{\rightarrow}\ensuremath{\infty} and U\ensuremath{\rightarrow}-\ensuremath{\infty}, 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 \ensuremath{\Vert}U\ensuremath{\Vert}\ensuremath{\sim}4, and agree with the variational estimate at U=0 within 10%.