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 $D^{eff}>\Delta$ region, the low energy properties are described by the Kondo state, where $\Delta$ is the hybridization width. As $D^{eff}$ decreases in this region, the Kondo temperature $T_K$ is enhanced, and its magnitude becomes comparable to $\Delta$ for $D^{eff}\sim \Delta$. In the $D^{eff}<\Delta$ region, the local singlet state between the electrons on the $f$ and ligand orbitals is formed.

5 pages, 3 figures, LaTeX, to be published in J. Phys. Soc. Jpn Vol. 67 No. 6

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