SINGLE-POLARON BAND-STRUCTURE OF THE HOLSTEIN MODEL

The single-polaron band structure of the Holstein model in one and two dimensions is studied using resummed strong-coupling perturbation the ory. Well-converged results are obtained for phonon frequencies of the order of the hopping integral and strong-to-intermediate electron-pho non coupling. The polaron band structure at intermediate coupling is s hown to deviate markedly from that of a nearest-neighbor tight-binding model and is in fact similar in shape to the prediction of weak-coupl ing self-consistent perturbation theory.