Anderson model out of equilibrium: conductance and Kondo temperature

TL;DR

This paper investigates the conductance and Kondo temperature in an out-of-equilibrium quantum dot system modeled by the Anderson model, using the NCA method to compare with equilibrium results and analyze temperature effects.

Contribution

It provides a detailed out-of-equilibrium analysis of conductance and Kondo temperature using the NCA approach, validating the method against linear response results.

Findings

Out-of-equilibrium conductance agrees with linear response results.

Conductance peaks at high temperatures and forms a plateau at low temperatures due to Kondo effect.

Different methods for determining Kondo temperature are compared.

Abstract

We calculate conductance through a quantum dot weakly coupled to metallic contacts by means of Keldysh out of equilibrium formalism. We model the quantum dot with the SU(2) Anderson model and consider the limit of infinite Coulomb repulsion. We solve the interacting system with the numerical diagrammatic Non-Crossing Approximation (NCA). We calculate the conductance as a function of temperature and gate voltage, from differential conductance (dI/dV) curves. We discuss these results in comparison with those from the linear response approach which can be performed directly in equilibrium conditions. Comparison shows that out of equilibrium results are in good agreement with the ones from linear response supporting reliability to the method employed. The discussion becomes relevant when dealing with general transport models through interacting regions. We also analyze the evolution of the curve of conductance vs gate voltage with temperature. While at high temperatures the conductance is peaked when the Fermi energy coincides with the energy of the localized level, it presents a plateau for low temperatures as a consequence of Kondo effect. We discuss different ways to determine Kondo's temperature and compare the values obtained in and out of equilibrium.