title: Density-matrix renormalization group study of pairing when electron-electron and electron-phonon interactions coexist: effect of the electronic band structure.
abstract: The density-matrix renormalization group is used to study the pairing when both electron-electron and electron-phonon interactions are strong in the Holstein-Hubbard model at half filling in a region intermediate between the adiabatic (Migdal's) and antiadiabatic limits. We have found (i) the pairing correlation obtained for a one-dimensional system is nearly degenerate with the charge density-wave correlation in a region where the phonon-induced attraction is comparable with the electron-electron repulsion, but (ii) pairing becomes dominant when we destroy the electron-hole symmetry in a trestle lattice. This provides an instance in which pairing can arise, in a lattice-structure dependent manner, from coexisting electron-electron and electron-phonon interactions.
authors.affiliation: Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Tezuka
authors.forename: Ryotaro
authors.initials: R
authors.lastname: Arita
authors.forename: Hideo
authors.initials: H
authors.lastname: Aoki