Dispersive Holstein model: which mass for the small polaron?

This numerical study of the Holstein model in the adiabatic regime shows that the small polaron properties are very sensitive to the lattice structure both in the ground state and at finite temperature. For weak intermolecular couplings, the polaronic effective masses md* are huge and depend strongly on the system dimensionality d. By increasing the coupling strength, md* becomes essentially d-independent and of the order of ≃10–50 times the electron mass. In this limit, however, the 1D and 2D polarons are still small while the 3D polaron broadens. The size of the polaron also depends on the degree of adiabaticity.