Non-Fermi liquid behavior in Kondo models

TL;DR

This paper reviews how certain generalized Kondo models exhibit non-Fermi liquid behavior at low energies, contrasting with the classic Fermi liquid theory, and discusses exact solutions revealing interacting many-body phenomena.

Contribution

It provides a comprehensive review of non-Fermi liquid behavior in generalized Kondo models and discusses exact solutions using Bethe ansatz and conformal field theory.

Findings

Generalized Kondo models show non-Fermi liquid behavior at low energies.

Exact solutions reveal interacting many-body processes.

Single electron scattering can produce multi-electron-hole states at zero energy.

Abstract

Despite the fact that the low energy behavior of the basic Kondo model cannot be studied perturbatively it was eventually shown by Wilson, Anderson, Nozieres and others to have a simple "local Fermi liquid theory" description. That is, electronic degrees of freedom become effectively non-interacting in the zero energy limit. However, generalized versions of the Kondo model involving more than one channel or impurity may exhibit low energy behavior of a less trivial sort which can, nonetheless, be solved exactly using either Bethe ansatz or conformal field theory and bosonization techniques. Now the low energy limit exhibits interacting many body behavior. For example, processes in which a single electron scatters off the impurity into a multi electron-hole state have a non-vanishing (and sometimes large) amplitude at zero energy. This corresponds to a rare solveable example of non-Fermi liquid behavior. Essential features of these phenomena are reviewed.