Self-Consistent Dynamical Theory for Valence Fluctuations

Abstract

The valence fluctuation phenomena in certain rare-earth systems involve a difficult many-body problem. The source of the difficulty is traced to subtle interaction effects between the localized 4f electrons and itinerant conduction electrons. The interaction often leads to the Kondo effect, but the outcome has several variants depending on each rare-earth system. In this paper we put forward a theory which can take detailed account of realistic 4f-shell structures and is expected to work both for the intermediate-valence (IV) and nearly integral-valence (Kondo) regimes. Since valence fluctuations in dilute rare-earth alloy systems are very similar to those in dense rare-earth compounds,¹ we concentrate here on single-site fluctuation processes and neglect the rare-earth intersite interactions.^{2, 3} We outline the theoretical formulation⁴ and report some numerical results⁵ on dynamical properties of Ce systems.