SPIN BLOCKADE IN NONLINEAR TRANSPORT THROUGH QUANTUM DOTS

The influence of excited levels on the non-linear-transport properties of a quantum dot weakly coupled to ideal leads is studied using a master-equation approach. A quantum-mechanical model for interacting electrons is used to determine the spectrum of the dot. The current-voltage characteristic shows Coulomb blockade and additional fine structure that is related to the excited states of the correlated electrons. Asymmetric coupling to the leads causes asymmetric conductance peaks. It is demonstrated that spin selection rules can lead to regions of negative differential conductance.