J. Phys.: Condens. Matter 44, 6639–6646 (2002)

SCI

Coherent potential approximation for charge ordering in the extended Hubbard model

H. A. Tuan, and P Thalmeier

We study charge ordering (CO) in the extended Hubbard model with both on-site and nearest-neighbour Coulomb repulsion (U and V, respectively) within the coherent potential approximation. The phase boundary between the homogeneous and charge-ordered phases for the square lattice is obtained for different values of U. It is shown that at quarter-filling for all values of U the CO exists only if the inter-site Coulomb repulsion V exceeds certain a critical value which is of the order of the kinetic energy t. Atfinite temperature a re-entrant transition is found in some region of V

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