Impurity systems fluctuating between two magnetic configurations: candidates for non Fermi-liquid behavior

TL;DR

This paper generalizes the impurity Anderson model for valence fluctuations between two magnetic states, revealing that the systems exhibit non-Fermi-liquid behavior due to an unstable strong-coupling fixed point.

Contribution

It introduces a generalized model for impurity valence fluctuations and analyzes its strong-coupling limit, predicting non-Fermi-liquid behavior in certain impurity systems.

Findings

Ground state degeneracy in most cases except extreme j-j coupling

Impurity magnetic moment is very small and overscreened

Strong-coupling fixed point is unstable, leading to non-Fermi-liquid behavior

Abstract

The appropriate generalization of the isotropic impurity Anderson model for valence fluctuations between two magnetic multiplets $l^n$ and $l^{n+1}$ is solved in the strong-coupling limit of Wilson's renormalization group for $l\leq$ 3. Except in the extreme case of $j-j$ coupling, the ground state is degenerate, the impurity magnetic moment is very small and is overscreened by the conduction electrons. The strong-coupling fixed point turns out to be unstable. Thus, at low enough temperatures the physics of the systems should be governed by an intermediate coupling fixed point and non Fermi-liquid behavior is expected.