Suppressing electron-phonon interactions in semiconductor quantum dot systems by engineering the electronic wavefunctions

Publication: Research - peer-reviewConference abstract in proceedings – Annual report year: 2012

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It is well-known that decoherence deteriorates the efficiency of cavity QED systems containing quantum dots (QDs), and that a major contribution stems from the coupling between the electrical carriers in the QD and acoustic phonons [1]. Employing a recently published model [2], we demonstrate how a proper matching between the electronic wavefuntion and the phonon-induced energy shift of valence and conduction band may be exploited to change the decoherence and decay properties of the QD by suppressing the phonon-induced processes.
This effect may be addressed in a photoluminescence experiment, where a CW laser excites a two-level QD which interacts with a non-Markovian reservoir of acoustical phonons, see Fig. 1a. We assume a simple harmonic confinement of the electronic carriers, resulting in Gaussian wavefunctions, (r) / exp[−r2/(2W2
)], withWe (Wg) being the width of the electron (hole) wavefunction. In Fig. 1b we plot the stationary QD population vs. the laser frequency. We observe that for non-equal electron and hole wavefunction, the phonon-induced effect on the population surprisingly is fully suppressed at specific detunings. In a coupled QD–cavity system [2, 3], see Fig. 2a, this effect causes the QD lifetime to be unaffected by phonon processes at specific QD-cavity detunings. Furthermore, as shown in Fig. 2b, a proper choice of the QD wavefunction minimizes the phonon-induced pure dephasing rate, both in terms of the short-time magnitude and the long-time constant value.
Furthermore we show, that even for realistic QDs, where We and Wg are determined by the QD shape and material composition, a significant suppression of phonon-induced processes is possible. Thus, more efficient quantum systems may be obtained if the QD wavefunctions are properly matched with the phononic properties of the surroundings.
Original languageEnglish
Title of host publication11th International Workshop on Nonlinear Optics and Excitation Kinetics in Semiconductors
Number of pages1
Publication date2012
Pages64
StatePublished

Conference

Conference11th International Workshop on Nonlinear Optics and Excitation Kinetics in Semiconductors (NOEKS)
CountryGermany
CityStuttgart
Period23/09/1227/09/12
Internet addresshttp://www.uni-stuttgart.de/noeks11

Bibliographical note

Poster presentation P9.

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