Finite-temperature exact diagonalization cluster dynamical mean-field study of the two-dimensional Hubbard model: Pseudogap, non-Fermi-liquid behavior, and particle-hole asymmetry

Ansgar Liebsch and Ning-Hua Tong
Phys. Rev. B 80, 165126 – Published 27 October 2009

Abstract

The effect of doping in the two-dimensional Hubbard model is studied within finite-temperature exact diagonalization combined with cluster dynamical mean-field theory. By employing a mixed basis involving cluster sites and bath molecular orbitals for the projection of the lattice Green’s function onto 2×2 clusters, a considerably more accurate description of the low-frequency properties of the self-energy is achieved than in a pure site picture. To evaluate the phase diagram, the transition from Fermi-liquid to non-Fermi-liquid behavior for decreasing hole doping is studied as a function of Coulomb energy, next-nearest-neighbor hopping, and temperature. The self-energy component ΣX associated with X=(π,0) is shown to develop a collective mode above EF, whose energy and strength exhibits a distinct dispersion with doping. This low-energy excitation gives rise to non-Fermi-liquid behavior as the hole doping decreases below a critical value δc, and to an increasing particle-hole asymmetry, in agreement with recent photoemission data. This behavior is consistent with the removal of spectral weight from electron states above EF and the opening of a pseudogap, which increases with decreasing doping. The phase diagram reveals that δc0.150.20 for various system parameters. For electron doping, the collective mode of ΣX(ω) and the concomitant pseudogap are located below the Fermi energy, which is consistent with the removal of spectral weight from the hole states just below EF. The critical doping, which marks the onset of non-Fermi-liquid behavior, is systematically smaller than for hole doping.

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  • Received 16 July 2009

DOI:https://doi.org/10.1103/PhysRevB.80.165126

©2009 American Physical Society

Authors & Affiliations

Ansgar Liebsch1 and Ning-Hua Tong2

  • 1Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich, Germany
  • 2Department of Physics, Renmin University of China, 100872 Beijing, China

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Issue

Vol. 80, Iss. 16 — 15 October 2009

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