Metallic Non-Fermi Liquid Phases of an Extended Hubbard Model in Infinite Dimensions

TL;DR

This paper investigates an extended Hubbard model in infinite dimensions, revealing novel non-Fermi liquid phases characterized by incoherent charge and spin excitations, distinct from traditional Fermi liquid behavior.

Contribution

It identifies and characterizes new non-Fermi liquid phases in an extended Hubbard model, including their impurity model counterparts, with detailed analysis of their incoherent metallic properties.

Findings

Discovery of three mixed valence states in impurity models.

Identification of non-Fermi liquid phases with incoherent charge and spin excitations.

Non-Fermi liquid phases occur over a wide parameter range.

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.