Asymmetric negative differential conductance in double quantum dots

An explanation for the recently observed asymmetric negative differential conductance (NDC) in a double-quantum-dot system attached to metallic external contacts is proposed. The NDC was observed only for one half of the bias voltage range (-V, V). The theory, which is based on a diagrammatic technique for non-equilibrium many-body operator Green functions, suggests that scattering between the states in the double quantum dot suppresses the total current dynamically as the bias voltage is increased. The effect is present in systems where the double-quantum-dot states are asymmetrically coupled to the left- and right-hand contacts, and we predict that a symmetric coupling will suppress the negative differential conductance completely.