Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 25: Poster Session: GaN - Optical Properties & Preparation and Characterization & Devices

HL 25.10: Poster

Monday, March 26, 2012, 16:00–19:00, Poster D

Long-range transport of indirect excitons by moving strain dots in a GaAs double quantum wells — •Snežana Lazić, Rudolf Hey, and Paulo Santos — Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany

We report on the acoustic transport of spatially indirect (inter-well) excitons in a GaAs/AlGaAs double quantum well. The photo-excited excitons are trapped within an array of moving strain dots with a spatial periodicity of a few µm. These dynamic potential dots are formed by interfering two surface acoustic waves (SAWs) propagating along orthogonal non-piezoelectric crystallographic directions. The trapping mechanism relies on a dynamic type-I modulation of the band edges via the deformation potential interaction. The exciton lifetime is voltage-tunable via the top semi-transparent gate and is substantially longer than the SAW period. We show that such system offers a controllable way for artificially producing cold exciton gases for the investigation of quantum collective effects.

Using spectrally and spatially resolved low-temperature photoluminescence measurements, we have observed the formation of a luminescence ring around the laser illumination spot, which is discussed in terms of thermalization of long-living indirect excitons. Under acoustic excitation, we demonstrate the long-range transport (of the order of 100 µm) followed by recombination at the inter-well exciton transition energy. These experiments allow us to determine the distribution of indirect excitons as well as to probe the exciton-exciton interactions within the dot array.