Out-of-equilibrium Kondo effect in double quantum dots

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 An derson Hamiltonian with interimpurity hopping. The Hamiltonian is solved by means of a nonequilibrium generalization of the slave-boson mean-held theo ry. It is demonstrated that measurements of the differential conductance dI /dV, far appropriate values of voltages and tunneling couplings, can give a direct observation of the coherent superposition between the many-body Kon do states of each dot. For large voltages and arbitrarily large interdot tu nneling, there is a critical voltage above which the physical behavior of t he system again resembles that of two decoupled quantum dots.