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