Slave spins away from half filling: Cluster mean-field theory of the Hubbard and extended Hubbard models

S. R. Hassan and L. de’ Medici
Phys. Rev. B 81, 035106 – Published 12 January 2010

Abstract

A slave-spin representation of fermion operators has recently been proposed for the half-filled single and multiband Hubbard model. We show that with the addition of a gauge variable, the formalism can be extended to finite doping. We solve the resulting spin problem using the cluster mean-field approximation. This approximation takes short-range correlations into account by exact diagonalization on the cluster, whereas long-range correlations beyond the size of clusters are treated at the mean-field level. In the limit where the cluster has only one site and the interaction strength U is infinite, this approach reduces to the Gutzwiller approximation. There are some qualitative differences when the size of the cluster is finite. We first compute the critical U for the Mott transition as a function of a frustrating nearest-neighbor interaction on lattices relevant for various correlated systems, namely, the cobaltates, the layered organic superconductors and the high-temperature superconductors. For the triangular lattice, we also study the extended Hubbard model with nearest-neighbor repulsion. In addition to a uniform metallic state, we find a (3)×(3) charge density wave in a broad doping regime, including commensurate ones. We find that in the large U limit, intersite Coulomb repulsion V strongly suppresses the single-particle weight of the metallic state.

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  • Received 9 May 2008

DOI:https://doi.org/10.1103/PhysRevB.81.035106

©2010 American Physical Society

Authors & Affiliations

S. R. Hassan1,2 and L. de’ Medici3,4

  • 1Department de Physique, Université de Sherbrooke, Québec, Canada J1K 2R1
  • 2The Institute of Mathematical Sciences, C.I.T. Campus, Taramani, Chennai 600113, India
  • 3Laboratoire de Physique des Solides, Université Paris-Sud-CNRS, UMR 8502, F-91405 Orsay Cedex, France
  • 4Dipartimento di Fisica, Università di Roma “La Sapienza,” Piazzale Aldo Moro 2, I-00185 Rome, Italy

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Vol. 81, Iss. 3 — 15 January 2010

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