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Spin-flip limited exciton dephasing in CdSe/ZnS colloidal quantum dots

Masia, Francesco ORCID: https://orcid.org/0000-0003-4958-410X, Accanto, Nicolo, Langbein, Wolfgang Werner ORCID: https://orcid.org/0000-0001-9786-1023 and Borri, Paola ORCID: https://orcid.org/0000-0002-7873-3314 2012. Spin-flip limited exciton dephasing in CdSe/ZnS colloidal quantum dots. Physical Review Letters 108 (8) , 087401. 10.1103/PhysRevLett.108.087401

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Abstract

The dephasing time of the lowest bright exciton in CdSe/ZnS wurtzite quantum dots is measured from 5 to 170 K and compared with density dynamics within the exciton fine structure using a sensitive three-beam four-wave-mixing technique unaffected by spectral diffusion. Pure dephasing via acoustic phonons dominates the initial dynamics, followed by an exponential zero-phonon line dephasing of 109 ps at 5 K, much faster than the ∼10  ns exciton radiative lifetime. The zero-phonon line dephasing is explained by phonon-assisted spin flip from the lowest bright state to dark-exciton states. This is confirmed by the temperature dependence of the exciton lifetime and by direct measurements of the bright-dark–exciton relaxation. Our results give an unambiguous evidence of the physical origin of the exciton dephasing in these nanocrystals.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Biosciences
Physics and Astronomy
Subjects: Q Science > Q Science (General)
Q Science > QC Physics
Publisher: American Physical Society
ISSN: 0031-9007
Funders: EPSRC
Last Modified: 07 Nov 2022 09:07
URI: https://orca.cardiff.ac.uk/id/eprint/33619

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