Study of nonequilibrium Kondo phenomenon via nonperturbative dynamical theory

TL;DR

This paper introduces a nonperturbative dynamical theory to analyze nonequilibrium Kondo phenomena, successfully explaining experimental observations of Kondo-peak splitting in mesoscopic systems.

Contribution

The authors develop a new nonperturbative dynamical approach for calculating Green's functions under nonequilibrium, specifically applied to the Kondo effect in quantum transport.

Findings

Successfully applied NDT to the Anderson model at equilibrium and nonequilibrium.

Explained Kondo-peak splitting as a splitting of a coherent peak under nonequilibrium.

Provided analytical and self-consistent numerical results matching experimental features.

Abstract

We develop a nonperturbative dynamical theory (NDT) to calculate the retarded Green's function under nonequilibrium conditions. The NDT is particularly useful for treating nonequilibrium transport problems in systems with strong correlation. We apply our NDT to the well-known single-impurity Anderson model at equilibrium to determine its feasibility. We then apply it to a nonequilibrium transport problem in a system with Kondo coupling. An Anderson model with two metallic reservoirs is studied to understand the phenomenon of Kondo-peak splitting in a single-electron transistor of mesoscopic size. We calculate the nonequilibrium retarded Green's function by using the NDT and analyze it in the atomic limit, where the novel coherent phenomenon manifested only under nonequilibrium conditions can be described in an analytical manner. We finally construct a self-consistent loop to calculate the retarded Green's function and present the results for spectral density and differential conductance obtained by the self-consistent method. Our results explain all the features of Kondo-peak splitting observed in experiments. One remarkable conclusion is that Kondo-peak splitting is not the splitting of a conventional Kondo peak, but the splitting of a novel coherent peak created under nonequilibrium steady-state conditions.