Andreev reflection in a triple quantum dot system coupled with a normal-metal and a superconductor

Abstract

Using the nonequilibrium green's function method, the electronic transport through a triple quantum dot system due to Andreev reflections (AR) is investigated theoretically. By adjusting systematic parameters, such as the interdot coupling and side-coupled dots' levels, we find that the AR conductance shows the Dicke effect in optics, in which the transition from subradiant state to superradiant state (and vice versa) takes place, and the AR transmission has the symmetric relation due to electron-hole symmetry. The property of the AR current versus the bias voltage is also discussed, the plateaus appear in the current graphics, and the interval and width of the plateaus are changed by tuning the interdot hopping and side-coupled dots' levels. This provides an efficient mechanism for controlling the conductance and current.