Kondo spectral functions at low-temperatures: A dynamical-exchange-correlation-field perspective

TL;DR

This paper presents a novel dynamical exchange-correlation field approach to accurately compute low-temperature spectral functions of the symmetric single impurity Anderson model, capturing key features like the Kondo resonance and Hubbard bands.

Contribution

It introduces a new formalism for the xc field that simplifies impurity problem calculations while maintaining high accuracy, especially in the Kondo regime.

Findings

The xc field captures both Hubbard side-bands and Kondo resonance.

The formalism works well in the thermodynamic limit and for finite clusters.

It offers a good balance between accuracy and computational complexity.

Abstract

We calculate the low-temperature spectral function of the symmetric single impurity Anderson model using a recently proposed dynamical exchange-correlation (xc) field formalism. The xc field, coupled to the one-particle Green's function, is obtained through analytic analysis and numerical extrapolation based on finite clusters. In the Kondo regime, the xc field is modeled by an ansatz that takes into account the different asymptotic behaviors in the small- and large-time regimes. The small-time xc field contributes to the Hubbard side-band, whereas the large-time to the Kondo resonance. We illustrate these features in terms of analytical and numerical calculations for small- and medium-size finite clusters, and in the thermodynamic limit. The results indicate that the xc field formalism provides a good trade-off between accuracy and complexity in solving impurity problems. Consequently, it can significantly reduce the complexity of the many-body problem faced by first-principles approaches to strongly correlated materials.