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- Murayama, A., et al.
(författare)
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Propagation dynamics of exciton spins in a high-density semiconductor quantum dot system
- 2009
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Ingår i: physica status solidi c. - : phys. stat. sol. c. - 1862-6351 .- 1610-1642.
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Konferensbidrag (refereegranskat)abstract
- We study propagation dynamics of exciton spins in a system composed of high-density self-assembled quantum dots (QDs) of CdSe and a diluted magnetic semiconductor (DMS) layer of ZnMnSe, where spin-polarized excitons are generated in the DMS layer and are subsequently injected into the QDs. The degree of circular polarization, P, of excitonic photoluminescence at 5 T in the coupled QDs shows a rapid increase with increasing delay time after a linearly polarized pulsed excitation, indicating the exciton-spin injection from the ZnMnSe to CdSe-QDs. The P value tends to decay gradually because of the exciton-spin relaxation in the QDs after the injection. The spin-polarized excitons in the QD ensemble migrate simultaneously from the QDs with higher exciton energies to those with lower exciton energies, where the exciton-spins relax inside each dot during the migration. Therefore, the observed P values in the QD emission band are affected by this feeding of the relaxed spins.
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| 2. |
- Murayama, A, et al.
(författare)
-
Transfer dynamics of spin-polarized excitons into semiconductor quantum dots
- 2009
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 129, s. 1927-1930
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Tidskriftsartikel (refereegranskat)abstract
- We study on the transfer dynamics of spin-polarized excitons into self-assembled quantum dots (QDs) of CdSe coupled with a diluted magnetic semiconductor (DMS) layer of ZnMnSe through a ZnSe barrier layer. A variation in the degree of circular polarization P of excitonic photoluminescence in the coupled QDs was observed between samples with different thicknesses (LB) of the non-magnetic barrier. Relatively high values of P (0.3) were obtained in the samples with LB=1 or 2 nm, and the time dependences of the P value indicate the spin-transfer dynamics. From the LB dependence of the spin-transfer time, the spin-transfer mechanism is discussed, namely spin-conserving energy transfer.
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