Build-up of the Kondo effect from real-time 2PI effective action for the Anderson impurity model

TL;DR

This paper demonstrates how the 2PI effective action approach can model the real-time development of the Kondo effect in a quantum dot, capturing its spectral resonance and response to external voltage.

Contribution

It introduces a nonperturbative 2PI effective action method to study the dynamical formation of the Kondo effect in the Anderson impurity model.

Findings

The 2PI approach captures the exponential suppression of the Kondo resonance width.

External voltage weakens the Kondo effect at the hybridization scale.

Different resummation schemes within 2PI are compared with other methods.

Abstract

The nonequilibrium time evolution of a quantum dot is studied by means of dynamic equations for time-dependent Greens functions derived from a two-particle-irreducible (2PI) effective action for the Anderson impurity model. Coupling the dot between two leads at different voltages, the dynamics of the current through the dot is investigated. We show that the 2PI approach is capable to describe the dynamical build-up of the Kondo effect, which shows up as a sharp resonance in the spectral function, with a width exponentially suppressed in the electron self coupling on the dot. An external voltage applied to the dot is found to deteriorate the Kondo effect at the hybridization scale. The dynamic equations are evaluated within different nonperturbative resummation schemes, within the direct, particle-particle, and particle-hole channels, as well as their combination, and the results compared with that from other methods.