Out-of-equilibrium Kondo effect in Double Quantum Dots

TL;DR

This paper investigates the out-of-equilibrium transport in double quantum dots in the Kondo regime, revealing how differential conductance measurements can directly observe Kondo state superpositions and identifying a critical voltage for decoupling behavior.

Contribution

It introduces a non-equilibrium slave-boson mean-field approach to analyze the Kondo effect in double quantum dots with interdot hopping, providing new insights into their transport properties.

Findings

Differential conductance can reveal superpositions of Kondo states.

A critical voltage exists where the system transitions to decoupled quantum dots.

At high voltages, the system exhibits two separate Kondo singularities.

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 interimpurity hopping. The hamiltonian is solved by means of a non-equilibrium generalization of the slave-boson mean-field theory. It is demonstrated that measurements of the differential conductance dI/dV, for the appropriate values of voltages and tunneling couplings, can give a direct observation of the coherent superposition between the many-body Kondo states of each dot. For large voltages and arbitrarily large interdot tunneling, there is a critical voltage above which the physical behaviour of the system is again that of two decoupled quantum dots, i.e two Kondo singularities pinned at each chemical potential.