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Luminescence Darkening of Strain-Trapped Excitons in Coupled Quantum Wells

Sinclair, Nicholas (2014) Luminescence Darkening of Strain-Trapped Excitons in Coupled Quantum Wells. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Interwell excitons in coupled quantum wells are a promising systems for achieving an excitonic Bose-Einstein condensate, as the extremely long lifetime of these excitations allow large populations to accumulate and thermal equilibration of the gas. Such a condensate would be notable for the constituent particles having strong, long-range, repulsive interactions, a property that also makes the condensate formation more difficult by suppressing wavefunction overlap. It is believed, however, that with suitable traps the bosonic nature of this excitation will prevail and a condensate will form. Within GaAs/AlGaAs coupled quantum wells, large-scale strain traps have been employed to confine excitons, and a transition is observed in the spatial structure of the exciton photoluminescence under conditions of high strain, low temperature, and high density. Under these conditions, the luminescence at the center of the trap, where the density remains largest, becomes dim compared to the rest of the trap region. This document presents evidence of this transition and explores the nature of the darkening by examining the exciton luminescence, resolved spatially, spectroscopically, and temporally. Several possible mechanisms for this behavior are discussed, in particular that of Bose-Einstein condensation, formation of an electron-hole liquid, and strain-induced valence-band mixing. However, none of these mechanisms adequately account for all of the behavior associated with the darkening. The valence-band mixing argument receives particular attention, as it presents the most testable predictions, in addition to offering an explanation for the darkening relying solely on the single-particle spectrum.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairSnoke, Davidsnoke@pitt.eduSNOKE
Committee MemberDevaty, Robertdevaty@pitt.eduDEVATY
Committee MemberChen, Kevinpec9@pitt.eduPEC9
Committee MemberLevy, Jeremyjlevy@pitt.eduJLEVY
Committee MemberCoalson, Rob Dcoalson@pitt.eduCOALSON
Date: 30 May 2014
Date Type: Publication
Defense Date: 16 April 2014
Approval Date: 30 May 2014
Submission Date: 28 March 2014
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 186
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Physics
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Indirect Excitons, Strain Trap, Coupled Quantum Wells, GaAs, Bose-Einstein condensate, Photoluminescence, Valence-Band Mixing, Interwell excitons
Date Deposited: 30 May 2014 12:22
Last Modified: 15 Nov 2016 14:18


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