Nonlinear Kondo transport through serially coupled double quantum dots

We study the transport property through the serially coupled double quantum dots (DQDs) system with Kondo resonance based on the dissipation equation of motion theory. A nonlinear behavior of the transport current is exhibited due to the competition between the interdot coupling strength of the two QDs and the Kondo effect. With the increase in interdot coupling strength, the transport current first increases at low interdot couplings and then decreases with the strong interdot couplings. The reason is that the interdot coupling strength will result in a continuous evolution from the Kondo singlet state of individual QDs to the spin singlet state forming between the two QDs. Moreover, we define the physical quantity ∂G/∂t as the differential function of differential conductance G with respect to interdot coupling strength t. The nonlinear transport behavior and the physical quantity ∂G/∂t with differential conductance at different bias voltages can be used to detect the potential Kondo resonance in the nonequilibrium transport experiments.