1/N-Expansion Study of aU-Finite Degenerate Anderson Model

Abstract

We propose a model convenient for studying properties of the degenerate Anderson models including finite intra-atomic Coulomb repulsion U by using the perturbation expansion from the large limit of the spin-orbital degeneracy N (1/ N -expansion). This is to extend a series of 1/ N -expansion studies on the U -infinite degenerate impurity and lattice Anderson models carried out by Nagoya group for including effects of finite U . As a first step, we study a case with a single Anderson impurity to investigate crossover behavior between magnetic state and non-magnetic state as a function of U by calculating average number of the localized electron, specific heat, charge susceptibility and spin susceptibility in the leading order of (1/ N ) and also the Kondo temperature and scattering rate of the conduction electrons up to the next leading order of (1/ N ).