Quantum Dots - Laboratory for Interacting Electron Systems

Interactions among electrons are responsible for many fascinating effects in condensed matter and atomic physics, from ferromagnetism to superconductivity.

We review our attempts at constructing a laboratory for interacting electron systems using semiconductor quantum dots. In this laboratory we assemble electron and exciton droplets one electron/exciton at a time and probe their electronic properties. The electron droplet assembled from a two-dimensional electron gas using metallic gates will be described. By connecting this droplet to spin polarised leads, the spin state of the droplet can be both manipulated and read. The technique reveals a number of nontrivial effects related to the number of electrons, their spin and their correlations.

Quantum dots enable us to not only look at electrons but also excitons in self-assembled quantum dots. We will show that the electron and hole complexes in these dots form excitonic artificial atoms. The principle underlying their electronic structure, hidden symmetry, bridges between the quantum dot and quantum Hall physics. These atoms are indeed artificial nano-structures without a counterpart in nature and offer interesting possibilities for designing quantum systems.

We conclude by summarising possible impact of quantum dots on nano-spintronics, nano-photonics, and quantum information.