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We analyze the two-dimensional extended Hubbard model (or d-p model) on a square lattice for fermion pairing by a slave boson method reported in a previous work[1]. The onsite coulomb repulsion between Cu d holes is assumed to be strong. The nearest-neighbor interaction in momentum space U(k, q), introduced additionally, for transition from a momentum q to k is taken to be separable and is expanded in terms of basis functions corresponding to mixed symmetry states involving dxy and dx2-y2 .Now additional holes are expected to occupy oxygen sites for the hole doping (δ>0) case. This implies that the renormalized charge transfer gap Δreg tends towards zero for δ >0.We find the approximate Fermi liquid behavior for Δreg →0 once the pure dx2-y2 wave singlet superconducting instability sets in; otherwise non-Fermi liquid behavior is the prevalent one. The charge and the spin ordering gaps appear in the single-particle excitation spectrum when dxy component is taken into account. The latter is expected to shed light on the pseudo-gap phenomenon in the normal state.
REFERENCE 1. Partha Goswami, Presented in SCES'07 proceedings and accepted for publication in Physica B. (see http://dx.doi.org/10.1016/j.physb 2007.10.076). |
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