TRANSPORT-PROPERTIES OF QUANTUM DOTS

Linear and nonlinear transport through ct quantum dot that is weakly c oupled to ideal quantum leads is investigated in the parameter regime where charging and geometrical quantization effects coexist. The exact eigenstates and spins elf a finite number of correlated electrons con fined within the dot are combined with a rate equation. The current is calculated in the regime of sequential tunnelling. The analytic solut ion far an Anderson impurity is given, The phenomenological charging m odel is compared with the quantum mechanical model for interacting ele ctrons. The current-voltage characteristics show Coulomb blockade. The excited states lead to additional fine-structure in the current volta ge characteristics. Asymmetry in the coupling between the quantum dot and the leads causes asymmetry in the conductance peaks which is rever sed with the bias voltage. The spin selection rules can cause a 'spin blockade' which decreases the current when certain excited states beco me involved in the transport. In two-dimensional dots, peaks in the li near conductance can be suppressed at tow temperatures, when the total spins of the corresponding ground states differ by more than 1/2. In a magnetic Field, an electron number parity effect due to the differen t spins of the many-electron ground states is predicted in addition to the vanishing of the spin blockade effect. All of the predicted featu res are consistent with recent experiments.