The Anderson impurity model with a narrow-band host: from orbital physics to the Kondo effect

TL;DR

This paper investigates the spectral properties of a particle-hole symmetric Anderson impurity model with a narrow-band host, revealing how orbital effects and the Kondo effect influence the spectral evolution across different interaction regimes.

Contribution

It provides accurate analytical results explaining spectral evolution in a narrow-band Anderson impurity model, connecting weak and strong coupling regimes with the Kondo effect.

Findings

Spectral evolution governed by orbital effects in weak coupling.

Smooth connection to the Kondo limit in strong coupling.

Analytical results explain the four-peak structure in spectra.

Abstract

A particle-hole symmetric Anderson impurity model with a metallic host of narrow bandwidth is studied within the framework of the local moment approach. The resultant single-particle spectra are compared to unrestricted Hartree-Fock, second order perturbation theory about the noninteracting limit, and Lanczos spectra by Hofstetter and Kehrein. Rather accurate analytical results explain the spectral evolution over almost the entire range of interactions. These encompass, in particular, a rationale for the four-peak structure observed in the low-energy sector of the Lanczos spectra in the moderate-coupling regime. In weak coupling, the spectral evolution is governed by orbital effects, while in the strong coupling Kondo limit, the model is shown to connect smoothly to the generic Anderson impurity with a flat and infinitely wide hybridization band.