Thursday, 01 November, 2007
Peculiar many-body effects revealed in the spectroscopy of highly charged quantum dots
M. Ediger, G. Bester, A. Badolato, P.M. Petroff, K. Karrai, A. Zunger, R.J. Warburton -Nature Phys. 3 (11): 774-779 (2007)
Coulomb interactions between electrons lead to the observed multiplet structure and breakdown of the Aufbau principle for atomic d and f shells(1). Nevertheless, these effects can disappear in extended systems. For instance, the multiplet structure of atomic carbon is not a feature of graphite or diamond. A quantum dot is an extended system
containing similar to 10(6) atoms for which electron-electron interactions do survive and the interplay between the Coulomb energy, J, and the quantization energy, Delta E, is crucial to Coulomb blockade(2-5). We have discovered consequences of Coulomb interactions in self-assembled quantum dots by interpreting experimental spectra with an atomistic calculation. The Coulomb effects, evident in the photon emission process, are tunable in situ by controlling the quantum dot charge from + 6e to -6e. The same dot shows two regimes: J <= Delta E for electron charging yet J similar to Delta E for hole charging. We find a breakdown of the Auf! bau principle for holes; clear proof of non-perturbative hole-hole interactions; promotion-demotion processes in the final state of the emission process, effects first predicted a decade ago(6); and pronounced configuration hybridizations in the initial state. The level of charge control and the energy scales result in Coulomb effects with no obvious analogues in atomic physics.