Spin Blockades in Electron Transport

Abstract

Linear and non—linear transport through a quantum dot weakly coupled to leads is investigated in the regime where charging and geometrical quantization effects are important. A master equation is combined with the exact quantum states of a finite number of strongly correlated electrons with spin inside the dot. The current—voltage characteristic of a quasi-one dimensional dot shows Coulomb blockade and additional finestructure that is related to the excited states of the electrons. Negative differential conductances occur due to spin selection rules that can lead to a ‘spin blockade’ which, in contrast to the Coulomb blockade, even reduces the current when the transport voltage is increased. In two dimensional dots spin effects can suppress linear conductance peaks at low temperatures.