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 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 in this region, indicating dominant superconducting pair correlations. We explore the full phase diagram as a function of Hubbard , phonon coupling constant, and phonon frequency.
- Received 7 May 2005
DOI:https://doi.org/10.1103/PhysRevLett.95.096401
©2005 American Physical Society