On virtual bound states in caesium and cerium

Abstract

This article reviews the work done a t Bangalore on some problems connected with the pressure-indudcd electronic phase transition in liquid caesium and the phenonknon of valence instability and related narrow band effects in cerium metal. Among the alkali metals, caesium exhibits striking anomalies in several of the physical properties a high pressures. A theoretical model for the phenomenon of electron collapse in the liquid phase is presented which is based on the concept of ' virtual bound state 1 or 'Scattering resonant@'. The result of the numerical calculations based on t h is model are given which generally explain all the main features of the anomalous resistivity behaviour of liquid caesium with pressure. I n the field of valence flectuating systems, new data on the pressure behaviour of the resistivity and the m - e lectric power in a typical Anderson lattice system like 3'-Ce are presented. The new observation of Kondo-like anomalies in 3/-ce and the irresonant enhancement with pressure are shown to favour the 4f virtual bound s t a t e model developed for cerium.