1/(N-1) expansion for a finite U Anderson model away from half-filling

TL;DR

This paper develops a 1/(N-1) expansion method for the SU(N) Anderson model away from half-filling, providing systematic corrections beyond the Hartree-Fock RPA and validating results against numerical renormalization group data.

Contribution

It introduces a systematic 1/(N-1) expansion scheme for the finite U Anderson model, extending the analysis beyond leading order and confirming its accuracy with N=4 NRG results.

Findings

Next-leading order results match N=4 NRG data closely.

The expansion scheme reliably predicts Fermi-liquid parameters for N>4.

The method uses standard Feynman diagrams and has broad applicability.

Abstract

We apply recently developed 1/(N-1) expansion to a particle-hole asymmetric SU(N) Anderson model with finite Coulomb interaction U. To leading order in 1/(N-1) it describes the Hartree-Fock random phase approximation (HF-RPA), and the higher-order corrections describe systematically the fluctuations beyond the HF-RPA. We show that the next-leading order results of the renormalized parameters for the local Fermi-liquid state agree closely with the numerical renormalization group results at N=4. It ensures the reliability of the next-leading order results for N>4, and we examine the N dependence of the local Fermi-liquid parameters. Our expansion scheme uses the standard Feynman diagrams, and has wide potential applications.