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Impact of environment on dynamics of exciton complexes in a WS2 monolayer

Jakubczyk, Tomasz, Nogajewski, Karol, Molas, Maciej R, Bartos, Miroslav, Langbein, Wolfgang, Potemski, Marek and Kasprzak, Jacek 2018. Impact of environment on dynamics of exciton complexes in a WS2 monolayer. 2D Materials 5 (3) , 031007. 10.1088/2053-1583/aabc1c

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Scientific curiosity to uncover original optical properties and functionalities of atomically thin semiconductors, stemming from unusual Coulomb interactions in the two-dimensional geometry and multi-valley band structure, drives the research on monolayers of transition metal dichalcogenides (TMDs). While recent works ascertained the exotic energetic schemes of exciton complexes in TMDs, we here infer their unusual coherent dynamics occurring on subpicosecond time scale. The dynamics is largely affected by the disorder landscape on the submicron scale, thus can be uncovered using four-wave mixing in the frequency domain, which enables microscopic investigations and imaging. Focusing on a WS2 monolayer, we observe that exciton coherence is lost primarily due to interaction with phonons and relaxation processes towards optically dark excitonic states. Notably, when temperature is low and disorder weak, excitons large coherence volume results in enhanced oscillator strength, allowing to reach the regime of radiatively limited dephasing. Additionally, we observe long valley coherence for the negatively charged exciton complex. We therefore elucidate the crucial role of exciton environment in the TMDs on its dynamics and show that revealed mechanisms are ubiquitous within this family.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: IOP Publishing: Hybrid Open Access
ISSN: 2053-1583
Date of First Compliant Deposit: 9 July 2018
Date of Acceptance: 6 April 2018
Last Modified: 10 Jul 2018 09:30

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