Non-sequential level filling in artifical atoms

Electrons in self-assembled InAs quantum dots (QDs) have been studied intensively in the past as model systems for strong three-dimensional carrier confinement. Charged with a small number of electrons they can be regarded as a versatile solid-state artificial atom. Our collaboration of researchers from the Ruhr-Universität Bochum, the UniversitätDuisburg-Essen and the High Field Magnet Laboratory succeeded to access electrically the quantized energy levels of such artificial atoms filled with a small number of holes. Using high magnetic fields to identify the individual energy levels we found a non-sequential filling of the atom-like shells resulting into a highly polarized ground state. These findings violate the normally observed sequential shell filling in atomic physic (Aufbau principle) and point towards a higher complexity of the strongly interacting few-hole system as compared to electrons in natural and artificial atoms.

The figure shows the charging energies for the InAs quantum dots filled with up to six holes as a function of the magnetic field. The number of holes in the dot and their orbital momentum for zero field is indicated on the left, the high-field orbital momentum for the N-hole ground state is given on the right. The insets show our proposed occupation of the single-particle levels for zero field and high fields.

This work was published in:

D. Reuter, P. Kailuweit, A.D. Wieck, U. Zeitler, O. Wibbelhoff, C. Meier, A. Lorke, and J.C. Maan
Coulomb-interaction induced incomplete shell filling in the hole system of InAs quantum dots
Physical Review Letters, 2005, Vol. 94, 026908.