NONLINEAR TRANSPORT-PROPERTIES OF QUANTUM DOTS

The influence of excited levels on nonlinear transport properties of a quantum dot weakly coupled to leads is studied using a master-equatio n approach. A charging model for the dot is compared with a quantum me chanical model for interacting electrons. The current-voltage curve sh ows Coulomb blockade and additional finestructure that is related to t he excited states of the correlated electrons. Unequal coupling to the leads causes asymmetric conductance peaks. Negative differential cond uctances are predicted due to the existence of excited states with dif ferent spins.