Nonequilibrium Perturbative Formalism and Spectral Function for the Anderson Model

TL;DR

This paper develops a nonequilibrium perturbative approach for the Anderson model, deriving self-energies up to fourth order, and connects real-time and imaginary-time formalisms, confirming the persistence of the Kondo resonance at low bias.

Contribution

It introduces a fourth-order nonequilibrium perturbative formalism for the Anderson model and links it with the equilibrium Matsubara approach.

Findings

Kondo resonance disappears at bias voltages above the Kondo temperature

The formalism accurately reproduces experimental observations

Self-energies are derived up to the fourth order

Abstract

The present work is based on the nonequilibrium perturbative formalism. There the self-energies are derived up to the forth-order. In consequence, it proves that the nonequilibrium (real-time) perturbative expansion can be connected with the Matsubara imaginary-time perturbative expansion for equilibrium. As the numerical results, the Kondo resonance still disappears for bias voltage exceeding the Kondo temperatures, as observed in experiments of two terminal systems.