Analytic impurity solver with the Kondo strong-coupling asymptotics

TL;DR

This paper introduces an analytic impurity solver for strongly correlated electrons that accurately captures Kondo physics and the metal-insulator transition by extending many-body perturbation theory with two-particle renormalizations.

Contribution

It develops a universal analytic impurity solver that extends perturbation theory to the critical regime, reproduces the Kondo scale, and clarifies the origin of the Kondo resonance.

Findings

Successfully reproduces the Kondo scale in the Anderson model

Identifies criteria for proper Kondo asymptotics in theories

Extends perturbation expansion to the metal-insulator transition

Abstract

We present an analytic universal impurity solver for strongly correlated electrons. We extend the many-body perturbation expansion via suitable two-particle renormalizations from the Fermi-liquid regime to the critical region of the metal-insulator transition. The reliability of the approximation in the strong-coupling limit is demonstrated by reproducing the Kondo scale in the single-impurity Anderson model. We disclose the origin of the Kondo resonance in terms of Feynman diagrams and find criteria for the existence of the proper Kondo asymptotic behavior in approximate theories.