Theory of Quantum Dot Transport

Abstract

Linear and non-linear transport through a quantum dot which is weakly coupled to leads is investigated in the parameter regime where charging and geometrical quantization effects can be important. The positions of the conductance peaks at low voltage depend only on differences between the many-electron ground state energies of the isolated dot for different particle numbers. At finite voltages, the excited levels of the dot can also influence the current. In order to calculate the current at arbitrary voltage, a master equation is combined with the exact quantum states of a finite number of strongly correlated electrons with spin inside the dot. We present results for two specific examples, namely quasi-one dimensional (1D) dots and 2D square dots. The current-volt age characteristic of a quasi-(1D) dot shows Coulomb blockade and additional finestructure that is related to the excited states of the electrons. Negative differential conductances occur due to states with different spins. Spin selection rules can lead to a ‘spin blockade’ which can reduce the current when the transport voltage is increased. In 2D square dots the qualitatively different electron spectrum leads to additional features as suppression of linear conductance peaks at low temperatures.