Unified description of Fermi and non-Fermi liquid behavior in a conserving slave boson approximation for strongly correlated impurity models

TL;DR

This paper presents a unified framework using a conserving slave boson approximation to describe Fermi and non-Fermi liquid behaviors in strongly correlated impurity models, accurately capturing infrared exponents.

Contribution

It introduces a conserving T-matrix approximation that reproduces exact infrared exponents with high accuracy, incorporating both spin and charge fluctuations.

Findings

Accurately recovers infrared exponents for impurity models.

Includes both coherent spin flip and charge fluctuation processes.

Bound state effects significantly alter low-energy behavior in single-channel cases.

Abstract

We show that the presence of Fermi or non-Fermi liquid behavior in the SU(N) x SU(M) Anderson impurity models may be read off the infrared threshold exponents governing the spinon and holon dynamics in a slave boson representation of these models. We construct a conserving T-matrix approximation which recovers the exact exponents with good numerical accuracy. Our approximation includes both coherent spin flip scattering and charge fluctuation processes. For the single-channel case the tendency to form bound states drastically modifies the low energy behavior. For the multi-channel case in the Kondo limit the bound state contributions are unimportant.