The asymmetric single-impurity Anderson model - the modified perturbation theory

TL;DR

This paper applies a modified perturbation theory to the single-impurity Anderson model, effectively capturing behaviors away from symmetry and revealing phenomena like local moment screening breakdown and susceptibility enhancement.

Contribution

It introduces and validates a modified perturbation approach for the Anderson model, especially effective in non-symmetric cases and crossover regimes.

Findings

Agreement with exact results in symmetric case

Breakdown of local moment screening with decreasing conduction band occupation

Enhanced zero-temperature susceptibility in crossover regime

Abstract

We investigate the single-impurity Anderson model by means of the recently introduced modified perturbation theory. This approximation scheme yields reasonable results away from the symmetric case. The agreement with exactly known results for the symmetric case is checked, and results for the non-symmetric case are presented. With decreasing conduction band occupation, the breakdown of the screening of the local moment is observed. In the crossover regime between Kondo limit and mixed-valence regime, an enhanced zero-temperature susceptibility is found.