Excitation spectra of the degenerate Anderson model with finite f-f Coulomb interaction

Abstract

Spectral densities of local single particle, magnetic and charge excitations are calculated for the impurity Anderson model based on the renormalization group approach. Calculations are made for various magnitudes of the f-f Coulomb interaction. The role of the multiplet splitting and of the so-called negative U interaction is also examined. The width of the peak at the Fermi level in the single particle spectrum has always a scale comparable to that of the magnetic excitation and is never larger than the hybridization width. The broad band-like peak in BIS of U-compounds is interpreted by a broad shoulder structure which appears when the f-f interaction is not small and the f-electron number is intermediate and larger than 1.