Dark States and Transport through Quantum Dots

Abstract

In quantum optics dark states and coherent population trapping are well known phenomenon, in which the states are decoupled from the laser and can no longer be excited into other states (in contrast to bright states). By analogy one can consider coherent trapping in electronic transport in a system of quantum dots [1]. In the regime of high bias voltage electron tunneling processes from/to the electrodes play the same role as the laser radiation and single-electron tunneling among quantum dots corresponds intra-atomic transitions. Destructive quantum interference can lead to coherent trapping with electronic dark states. More recently, the e ects of the dark states on transport through triple and quadruple dots was analyzed using the methods of the general master equation [1] and the diagonal master equation [2, 3]. In this paper we want to study dark state conditions in the presence of small and large electric eld for triple and quadruple dots for di erent orientation of an external electric eld. We restrict our considerations to the case with a single electron in the system and just one level on each dot in an in nite bias limit.