Effect of Coulomb charging energy on electron oscillations in a coupled-quantum-dot structure

The effect of the Coulomb charging energy on the time evolution of the electron wave packet in a coupled-quantum-dot structure is investigated by use of coupled equations derived from the Schrödinger equation. As long as the Coulomb charging energy does not exceed a certain threshold energy (four times as much as the coupling energy between the dots), the electron wave packet, which was initially localized in one of the dots, is completely transferred to the other dot and oscillates back and forth between the two dots. If the Coulomb charging energy exceeds the threshold, the transfer rate of the wave packet becomes abruptly incomplete and is reduced to less than one-half. This effect may be called the Coulomb blockade of the resonant electron tunneling in coupled quantum dots. It should be stressed that the transfer period of the wave packet is remarkably increased at and near the threshold charging energy. The analysis presented here should provide a useful basis for the design and evaluation of mesoscopic devices operating with coupled quantum structures.