One-dimensional Holstein model revisited

We analyze the global ground-state (quantum) phase diagram of the one-dimensional spinful Holstein model at half filling as a function of the strength of the electron-phonon coupling (represented by the strength of the phonon-induced attraction, U) and the phonon frequency co0. In addition to reanalyzing the various asymptotic regimes, we carry out density-matrix renormalization group simulations to correct previous inferences concerning the antiadiabatic (large co0) and strong-coupling (large U) regimes. There are two distinct phases-a fully gapped commensurate charge-density-wave phase and a spin-gapped Luther-Emery phase with a gapless charge mode-separated by a phase boundary, with a shape that reflects different microscopic physics in the weak- and strong-coupling limits.