title: Efficient dynamical mean field simulation of the Holstein-Hubbard model.
abstract: We present a method for solving impurity models with electron-phonon coupling, which treats the phonons efficiently and without approximations. The algorithm is applied to the Holstein-Hubbard model in the dynamical mean field approximation, where it allows access to strong interactions, very low temperatures, and arbitrary fillings. We show that a renormalized Migdal-Eliashberg theory provides a reasonable description of the phonon contribution to the electronic self-energy in strongly doped systems, but fails if the quasiparticle energy becomes of order of the phonon frequency.
authors.affiliation: Columbia University, New York, NY 10027, USA.
authors.forename: Philipp
authors.initials: P
authors.lastname: Werner
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Millis