CURRENT RESPONSE OF QUANTUM-DOT MODULATED BY TIME-DEPENDENT EXTERNAL FIELDS

We study how the de transport through a semiconductor quantum dot vari es when time-dependent external fields are applied. We find (i) the sh ift of the Coulomb blockade region due to the interband excitation, (i i) the resonant peak structures of the Coulomb oscillation due to the intraband excitation, and (iii) the electron pumping effect in the qua ntum dot modulated by the microwave field with frequency lower than th e level spacing of the quantum dot.