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Coherent dynamics in InGaAs quantum dots and quantum dot molecules

Langbein, Wolfgang Werner, Borri, Paola, Woggon, U., Schwab, M., Bayer, M., Fafard, S., Wasilewski, Z., Hawrylak, P., Stavarache, V., Reuter, D. and Wieck, A. D. 2005. Coherent dynamics in InGaAs quantum dots and quantum dot molecules. Physica E: Low-dimensional Systems and Nanostructures 26 (1-4) , pp. 400-407. 10.1016/j.physe.2004.08.004

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We measure the dephasing time of the exciton ground state transition in InGaAs quantum dots (QD) and quantum dot molecules (QDM) using a sensitive four-wave mixing technique. In the QDs we find experimental evidence that the dephasing time is given only by the radiative lifetime at low temperatures. We demonstrate the tunability of the radiatively limited dephasing time from 400 ps up to 2 ns in a series of annealed QDs with increasing energy separation of 69–330 meV from the wetting layer continuum. Furthermore, the distribution of the fine-structure splitting ℏδ1ℏδ1 and of the biexciton binding energy ℏδBℏδB is measured. ℏδ1ℏδ1 decreases from 96 to View the MathML source6μeV with increasing annealing temperature, indicating an improving circular symmetry of the in-plane confinement potential. The biexciton binding energy shows only a weak dependence on the confinement energy, which we attribute to a compensation between decreasing confinement and decreasing separation of electron and hole. In the QDM we measured the exciton dephasing as function of interdot barrier thickness in the temperature range from 5 to 60 K. At 5 K dephasing times of several hundred picoseconds are found. Moreover, a systematic dependence of the dephasing dynamics on the barrier thickness is observed, showing how the quantum mechanical coupling in the molecules affects the exciton lifetime and acoustic-phonon interaction.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QC Physics
Uncontrolled Keywords: Quantum dots; Dephasing; Four-wave mixing; Coupled quantum dots; Exciton fine-structure; Biexcitons
Publisher: Elsevier
ISSN: 1386-9477
Last Modified: 13 May 2019 20:38

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