Momentum average approximation for models with electron-phonon coupling dependent on the phonon momentum

Abstract

We generalize the momentum average (MA) approximation to study the properties of models with momentum-dependent electron-phonon coupling. As in the case of the application of the original MA to the Holstein model, the results are analytical, numerically trivial to evaluate, exact for both zero bandwidth and for zero electron-phonon coupling, and are accurate everywhere in parameter space. Comparison with available numerical data confirms this accuracy. We then show that further improvements can be obtained based on variational considerations, using the one-dimensional breathing-mode Hamiltonian as a specific example. For example, by using this variational MA, we obtain ground state energies within at most 0.3% error of the numerical data.

15 pages, 10 figures

References in corpus (7)

• Green's function of a dressed particle
• The Green's Function of the Holstein Polaron
• Systematic improvement of the Momentum Average approximation for the Green's function of a Holstein polaron
• Temperature dependence of the angle resolved photoemission spectra in the undoped cuprates: self-consistent approach to the t-J-Holstein model
• Spectral Properties of Holstein and Breathing Polarons
• Survival of the Dirac points in rippled graphene
• Holstein polaron: the effect of multiple phonon modes