Estimate of the polaron mass in high-T-c superconductors

I study the motion of polarons as a function of temperature in the context of a molecular crystal model in which the discreteness of the lattice is ac counted for. The model is based on a non linear Schrodinger equation which can be solved perturbatively if the conditions for the existence of small p olarons are assumed. The polaron bandwidth and the site jump hopping probab ility have been calculated versus temperature and dimensionality. The cross over temperature T-d* between band-like and hopping motion is reduced in lo w-dimensional systems due to the enhanced importance of the off-diagonal sc attering processes. An Einstein phonon spectrum leads to wrong estimates of the polaron bandwidths. The first and second neighbors intermolecular forc e constants which parametrize the pair interactions strongly affect the val ues of the ground state polaron bandwidth and of the hopping probability. W e discuss the relevance of the model to high-T-c, superconductors in which polaronic features in the transport properties have been pointed out [1]. T he estimated effective polaron masses are consistent with T-c values of ord er similar or equal to 100 K. (C) 1999 Elsevier Science B.V. All rights res erved.