Solution of the Multi-Channel Anderson Impurity Model: Ground state and thermodynamics

TL;DR

This paper solves the SU(N) x SU(M) Anderson impurity model using Bethe-Ansatz, revealing detailed thermodynamics and ground state properties across temperature regimes, including non-Fermi-liquid behavior.

Contribution

It extends the Bethe-Ansatz formalism to solve the multi-channel Anderson model and characterizes its ground state and thermodynamics across all temperature ranges.

Findings

Identifies different valence fluctuation regimes at various temperatures.

Derives impurity entropy, charge valence, and specific heat over full temperature range.

Shows low-energy physics governed by a line of fixed points indicating non-Fermi-liquid behavior.

Abstract

We present the solution of the SU(N) x SU(M) Anderson impurity model using the Bethe-Ansatz. We first explain what extensions to the formalism were required for the solution. Subsequently we determine the ground state and derive the thermodynamics over the full range of temperature and fields. We identify the different regimes of valence fluctuation at high temperatures, followed by moment formation or intrinsic mixed valence at intermediate temperatures and a low temperature non-Fermi liquid phase. Among other things we obtain the impurity entropy, charge valence and specific heat over the full range of temperature. We show that the low-energy physics is governed by a line of fixed points. This describes non-Fermi-liquid behavior in the integral valence regime, associated with moment formation, as well as in the mixed valence regime where no moment forms.