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Coherence and density dynamics of excitons in a single-layer MoS2 reaching the homogeneous limit

Jakubczyk, Tomasz, Nayak, Goutham, Scarpelli, Lorenzo, Liu, Wei-Lai, Dubey, Sudipta, Bendiab, Nedjma, Marty, Laëtitia, Taniguchi, Takashi, Watanabe, Kenji, Masia, Francesco, Nogues, Gilles, Coraux, Johann, Langbein, Wolfgang, Renard, Julien, Bouchiat, Vincent and Kasprzak, Jacek 2019. Coherence and density dynamics of excitons in a single-layer MoS2 reaching the homogeneous limit. ACS Nano 13 (3) , pp. 3500-3511. 10.1021/acsnano.8b09732

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Abstract

We measure the coherent nonlinear response of excitons in a single layer of molybdenum disulfide embedded in hexagonal boron nitride, forming a h-BN/MoS2/h-BN heterostructure. Using four-wave mixing microscopy and imaging, we correlate the exciton inhomogeneous broadening with the homogeneous one and population lifetime. We find that the exciton dynamics is governed by microscopic disorder on top of the ideal crystal properties. Analyzing the exciton ultrafast density dynamics using amplitude and phase of the response, we investigate the relaxation pathways of the resonantly driven exciton population. The surface protection via encapsulation provides stable monolayer samples with low disorder, avoiding surface contaminations and the resulting exciton broadening and modifications of the dynamics. We identify areas localized to a few microns where the optical response is totally dominated by homogeneous broadening. Across the sample of tens of micrometers, weak inhomogeneous broadening and strain effects are observed, attributed to the remaining interaction with the h-BN and imperfections in the encapsulation process.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Biosciences
Additional Information: This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.
Publisher: American Chemical Society
ISSN: 1936-0851
Date of First Compliant Deposit: 4 September 2019
Date of Acceptance: 2 February 2019
Last Modified: 04 Sep 2019 12:06
URI: http://orca-mwe.cf.ac.uk/id/eprint/124739

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