Hubbard model with orbital degeneracy and integer or noninteger filling

TL;DR

This paper investigates how orbital degeneracy and valence affect the electronic properties of the Hubbard model, revealing that degeneracy broadens the spectrum and reduces charge contributions to specific heat, with deviations from integer valence narrowing the spectrum.

Contribution

It provides new insights into the effects of orbital degeneracy and valence on spectral and thermodynamic properties in the Hubbard model with small clusters.

Findings

Degeneracy increases the photoemission spectrum width.

Degeneracy reduces charge contribution to specific heat.

Non-integer valence narrows the spectrum.

Abstract

The photoemission spectrum and the specific heat are studied in the Hubbard model of small clusters including orbital degeneracy. We focus on the degeneracy and valence dependence in the limit of a large Coulomb interaction. For integer valence, it is found that the degeneracy increases the width of the photoemission spectrum and it reduces the contribution from the charge degrees of freedom to the specific heat. A deviation from integer valence reduces the width of the photoemission spectrum.