Properties of the Hubbard Hamiltonian including the resonance-broadening terms for an arbitrarily filled band

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Abstract
In this paper, resonance broadening is included along with spin-disorder scattering to study the properties of the Hubbard Hamiltonian. Our solution, obtained through use of the locator technique, is valid for all strengths of the Coulomb repulsion term and for all band occupancies. However, here we restrict our work to the strong-correlation limit. We find that inclusion of the resonance-broadening terms (in particular spin-flip scattering) leads to qualitative differences in the pseudoparticle density of states compared with the density of states obtained with spin-disorder scattering only. When all three of Hubbard's scattering terms are included, the ground state is nonferromagnetic for any level of band filling. We also calculate the specific heat, magnetic susceptibility, and spin-spin correlation function as a function of temperature. Partial band occupancy yields a Pauli-like susceptibility at low temperature that transforms smoothly to Curie-like behavior at high temperature. The specific heat exhibits one or two maxima depending on occupancy, but these maxima are not reflected in the susceptibility and seem to be associated, not with magnetic ordering transitions, but with excitations across the Mott-Hubbard gap.