Peierls-Holstein dimer model with coherent, squeezed oscillatory trial functions

The Holstein-Peierls model for a dimer is a very simple description of a tight-binding electron (or exciton) coupled at each site to an optical phonon. We study this problem in a region of parameter space where the three relevant physical quantities, the hopping integral - |t|, the optical phonon frequency Ω and the electron-phonon coupling constant g are of comparable magnitude. We obtain a non-perturbative solution by using a unitary transformation and a variational ansatz in terms of squeezed phonon states. The polaron effective mass behaves very differently at the boundaries of the tight-binding band. We also calculate the mean square amplitudes of the relevant phonon momentum and position variables for our solution. © 1998 Elsevier Science B.V. All rights reserved.