Influence of microwave fields on electron transport through a quantum dot in the presence of direct tunneling between leads

We consider the time-dependent electron transport through a quantum dot coupled to two leads in the presence of the additional overdot (bridge) tunneling channel. By using the evolution operator method together with the wide-band limit approximation we derived the analytical formulas for the quantum dot charge and current flowing in the system. The influence of the external microwave field on the current and the derivatives of the current with respect to the gate and source-drain voltages has been investigated for a wide range of parameters. The most characteristic feature of including the additional overdot tunneling channel is an asymmetric behavior of the function describing the dependence of the average current vs the gate voltage or the differential conductance vs the source-drain voltage.