Kondo effect in coupled quantum dots: a Non-crossing approximation study

TL;DR

This paper theoretically investigates the Kondo effect in coupled quantum dots using a generalized non-crossing approximation, providing predictions for experimental transport measurements and demonstrating how coherence between Kondo states can be observed.

Contribution

It introduces a novel application of the NCA to coupled quantum dots in the Kondo regime and offers benchmark calculations for their transport properties.

Findings

Differential conductance measurements can reveal Kondo state coherence.

Linear conductance vs temperature shows a non-monotonic behavior with a maximum at T*.

Predictions enable experimental detection of quantum coherence in coupled quantum dots.

Abstract

The out-of-equilibrium transport properties of a double quantum dot system in the Kondo regime are studied theoretically by means of a two-impurity Anderson Hamiltonian with inter-impurity hopping. The Hamiltonian, formulated in slave-boson language, is solved by means of a generalization of the non-crossing approximation (NCA) to the present problem. We provide benchmark calculations of the predictions of the NCA for the linear and nonlinear transport properties of coupled quantum dots in the Kondo regime. We give a series of predictions that can be observed experimentally in linear and nonlinear transport measurements through coupled quantum dots. Importantly, it is demonstrated that measurements of the differential conductance ${\cal G}=dI/dV$, for the appropriate values of voltages and inter-dot tunneling couplings, can give a direct observation of the coherent superposition between the many-body Kondo states of each dot. This coherence can be also detected in the linear transport through the system: the curve linear conductance vs temperature is non-monotonic, with a maximum at a temperature $T^*$ characterizing quantum coherence between both Kondo states.