Effect of electron - Elecron interactions in a quantum dot with a tapered constriction

We study the effect of electron - electron interactions between several electrons in a quantum dot with a tapered constriction by monitoring the behavior of the position of the absolute charge density maximum, Zmax, of each occupied state under DC electric fields. States of this system are localized in, and can be identified with, either the left-or right-hand region, separated by the neck of the constriction. To demonstrate the effect, two cases with three electrons in the quantum dot were studied: (1) One electron is in the left-hand side region and the other two electrons are in the right-hand side region. They occupy the two lowest energy states of the quantum dot system. The movement of the Zmax of the singly occupied state through the constriction does not show any unusual behavior except that it can be accelerated by a resonance process. (2) All three electrons are in the left-hand side region and occupy the two lowest energy states in that region. In this case, the Zmax's of the two states move through the constriction in a competitive manner which would not be anticipated on the basis of either energy considerations or the results of case 1. Furthermore, and most significantly, we show that this unusual behavior depends completely upon electron - electron interactions: if they are not taken into account, it does not occur. We show also that this competitive process can occur in a ground-state configuration. © 1997 Academic Press Limited.