Renormalization of the electron-phonon interaction in the Hubbard model

摘要

We calculate the electron-phonon vertex in the two-dimensional Hubbard model by a strong coupling approach based on cumulant expansion. The role of the on-site Coulomb interaction on the coupling of the electrons to the Holstein phonons is investigated in different regions of the Brillouin zone. The results reveal the presence of a strong forward scattering and an effective increase of the vertex function at low temperatures above a certain critical U. Comparison with other approaches is also discussed. (c) 2005 Elsevier B.V. All rights reserved.