Equation of motion approach to the solution of Anderson model

TL;DR

This paper reexamines the single impurity Anderson model using an equation of motion approach, introducing a systematic truncation scheme that improves the accuracy of the Kondo temperature and density of states calculations.

Contribution

It develops a uniform truncation scheme for Green functions via cluster expansions, correcting previous approximations and enhancing quantitative results.

Findings

Corrects the missing factor of two in the Kondo temperature estimate

Achieves a more accurate density of states at the Fermi level

Provides a systematic framework for Green function calculations in SIAM

Abstract

Based on an equation of motion approach the single impurity Anderson model(SIAM) is reexamined. Using the cluster expansions the equations of motion of Green functions are transformed into the corresponding equations of motion of connected Green functions, which provides a natural and uniform truncation scheme. A factor of two missing in the Lacroix's approximation for the Kondo temperature is gained in the next higher order truncation beyond Lacroix's. A quantitative improvement in the density of states at the Fermi level is also obtained.