Single Impurity Anderson Model with Coulomb Repulsion between Conduction Electrons on the Nearest-Neighbour Ligand Orbital

Abstract

We study how the Kondo effect is affected by the Coulomb interaction between conduction electrons on the basis of a simplified model. The single impurity Anderson model is extended to include the Coulomb interaction on the nearest-neighbour ligand orbital. The excitation spectra are calculated using the numerical renormalization group method.The effective bandwidth on the ligand orbital, D^eff, is defined to classify the state. This quantity decreases as the Coulomb interaction increases. In the D^eff > Δ region, the low energy properties are described by the Kondo state, where Δ is the hybridization width. As D^eff decreases in this region, the Kondo temperature T_K is enhanced, and its magnitude becomes comparable to Δ for D^eff -- Δ. In the D^eff < Δ region, the local singlet state between the electrons on the f and ligand orbitals is formed.