Metallic non-Fermi-liquid phases of an extended Hubbard model in infinite dimensions.

Abstract

We study an extended Hubbard model in the limit of infinite dimensions and its zero dimensional counterpart, a generalized asymmetric Anderson model. In the impurity model we find three kinds of mixed valence states: a) the usual strong coupling state in which a resonance forms at the Fermi level; b) a weak coupling state in which neither the impurity spin nor the impurity charge degrees of freedom is quenched; and c) an intermediate coupling state where the spin but not the charge degree of freedom is quenched. The corresponding phases of the extended Hubbard model in infinite dimensions are a) a Fermi liquid; b) a non-Fermi liquid state with incoherent charge and spin excitations; and c) a non-Fermi liquid state with incoherent charge but coherent spin excitations. The non-Fermi liquid phases are incoherent metallic states with vanishing quasiparticle residue, self-similar local correlation functions, and asymptotically decoupled charge and spin excitations. The non-Fermi liquid phases occur for a wide range of parameters.