CHARGING EFFECTS IN ULTRASMALL QUANTUM DOTS IN THE PRESENCE OF TIME-VARYING FIELDS

The influence of charging effects on time-dependent transport in small semiconductor quantum dots with arbitrary level spectra is studied. S tarting from an explicit time-dependent tunnelling Hamiltonian, a non- Markovian master equation is derived which is also valid in the nonlin ear response regime. The many-body nonequilibrium distribution functio ns of the dot are calculated and the I-V characteristic of the structu re including the displacement currents is obtained. New resonant featu res show up in the Coulomb oscillations and in the Coulomb staircase, and a new possibility to realize electronic pumps is described.