Title: Exotic electronic states in semiconductor quantum dots
Abstract: Quantum correlations among electrons confined in semiconductor quantum dots (QDs) are expected to lead to exotic states of matter, such as an electron molecule. In the limit of vanishing electron density, the distances between confined electrons are rigidly fixed like those of nuclei in conventional molecules. The electronic excitations of such a molecule are quantized normal modes of roto-vibration, whose quanta have either a rigid-rotor or relative-motion character. I will present a joint experimental and theoretical investigation of the neutral electronic excitations of nanofabricated AlGaAs/GaAs QDs that contain four electrons. We use inelastic light scattering to probe electronic charge and spin excitations in an array of identical fabricated QDs. Spectra of low-lying excitations associated with charges of the relative-motion wave function - the analogues of the vibrational modes in aconventional molecule - do not depend on the rotational state represented by the angular momentum, which can be controlled by a magnetic field. A theoretical model, based on full configuration-interaction method, offers an excellent quantitative agreement with the experimental findings.
