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Strain-induced darkening of trapped excitons in coupled quantum wells at low temperature
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Sinclair, N. W., Wuenschell, J. K., Vörös, Z., Nelsen, B., Snoke, D. W., Szymanska, M. H. (Marzena H.), Chin, A. (Alex), Keeling, J. (Jonathan), Pfeiffer, L. and West, K. W. (2011) Strain-induced darkening of trapped excitons in coupled quantum wells at low temperature. Physical Review B (Condensed Matter and Materials Physics), Vol.83 (No.24). p. 245304. doi:10.1103/PhysRevB.83.245304 ISSN 1098-0121.
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Official URL: http://dx.doi.org/10.1103/PhysRevB.83.245304
Abstract
In GaAs/AlGaAs coupled quantum wells, strain-induced traps may be used to confine excitons in in-plane, harmonic traps. Using these traps, we have pursued Bose-Einstein condensation (BEC) of long-lived, spatially indirect excitons. Here, we report a remarkable transition of the indirect exciton luminescence pattern with increasing strain, increasing exciton density, and decreasing temperature, to a spatial pattern exhibiting a large dark spot at the trap center, where we expect the exciton density to be maximum. The mechanism of particle loss is ruled out as an explanation for this dark spot. While the onset criteria are approximately consistent with the conditions for BEC of a weakly interacting gas, the conspicuous proximity in energy of the indirect light-hole states suggests that an explanation employing the single-particle physics of light-hole-heavy-hole mixing may explain the phenomenon. The effect of the strain is modeled, and the resulting landscape of indirect exciton spin states is discussed. The relative oscillator strengths of these states are predicted by an exact numerical solution of the two-particle Schrodinger equation for electrons and holes in coupled quantum wells and an electric field. The contrast in oscillator strengths is sufficient to produce this luminescence pattern, but this analysis suggests a strongly diminished lifetime as stress is increased. The opposite lifetime dependence is observed experimentally. Additionally, the temperature dependence eludes explanation by this mechanism.
Item Type: | Journal Article | ||||
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Subjects: | Q Science > QC Physics | ||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||
Library of Congress Subject Headings (LCSH): | Bose-Einstein condensation, Polaritons, Quantum wells | ||||
Journal or Publication Title: | Physical Review B (Condensed Matter and Materials Physics) | ||||
Publisher: | American Physical Society | ||||
ISSN: | 1098-0121 | ||||
Official Date: | 9 June 2011 | ||||
Dates: |
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Volume: | Vol.83 | ||||
Number: | No.24 | ||||
Page Range: | p. 245304 | ||||
DOI: | 10.1103/PhysRevB.83.245304 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Restricted or Subscription Access | ||||
Funder: | United States. Dept. of Energy | ||||
Grant number: | DE-FG02-99ER457080 (DOE) |
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