Few-electron quantum dot molecules

Abstract

Semiconductor quantum dots have been studied for nearly two decades with a variety of experimental and theoretical methods. The typical dimensions of these "artificial atoms" are from a hundred nanometers to one micrometer and the number of electrons inside the quantum dots can range from one to several hundred. The tunable size, shape and electron number, as well as the enhanced electron correlation and magnetic field effects, makes quantum dots excellent objects for studying fascinating many-electron quantum physics in a controlled way. In the rapidly growing fields of nanoscience and nanotechnology, quantum dots are promising candidates for future nanoelectronic devices. One of the most intriguing scenarios of quantum dot applications lies in the utilization of an electron spin as a quantum bit in quantum computing.

This Thesis deals with the modeling of electron states in two-dimensional coupled quantum dots or quantum-dot molecules. The emphasis is on describing electron correlations properly but concentrating only on a few electrons inside the quantum-dot molecules. In this Thesis we mostly consider two interacting electrons and find remarkably complex behavior as a function of the magnetic field. We find the electron-electron interactions and the shape of the confining potential to have a profound effect on the two-electron quantum states.

The main results of this Thesis are the calculations and analysis of the quantum-mechanical states of two electrons in a magnetic field. This includes the ground-state transitions and magnetizations of the system as a function of magnetic field and careful analysis of the wave functions and the calculation and analysis of the far-infrared magneto-optical absorption spectra. We also study classical electrons in a quantum-dot molecule. This is relevant for the Wigner crystallization of electrons in a very high magnetic field or in a very low electron density.