title: Intermediate phase of the one dimensional half-filled Hubbard-Holstein model.
abstract: We present a numerical study of the Hubbard-Holstein model in one dimension at half filling, including finite-frequency quantum phonons. At half filling, the effects of the electron-phonon and electron-electron interactions compete with the Holstein phonon coupling acting as an effective negative Hubbard on-site interaction U that promotes on-site electron pairs and a Peierls charge-density wave state. Most previous work on this model has assumed that only Peierls or Mott phases are possible at half filling. However, there has been speculation that a third metallic phase exists between the Peierls and Mott phases. We confirm the intermediate phase, and show that the Luttinger liquid correlation exponent K(rho) >1 in this region, indicating dominant superconducting pair correlations. We explore the full phase diagram as a function of Hubbard U, phonon coupling constant, and phonon frequency.
authors.affiliation: Department of Physics and Astronomy and ERC Center for Computational Sciences, Mississippi State University, Mississippi State, MS 39762, USA.
authors.forename: R T
authors.initials: RT
authors.lastname: Clay
authors.forename: R P
authors.initials: RP
authors.lastname: Hardikar