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The energy landscape of optical excitations in mono- and few-layer transition metal dichalcogenides (TMDs) is dominated by optically bright and dark excitons. These excitons can be fully localized within a single TMD layer, or the electron- and the hole-component of the exciton can be charge-separated over multiple TMD layers. Such intra- or interlayer excitons have been characterized in detail using all-optical spectroscopies, and, more recently, photoemission spectroscopy. In addition, there are so-called hybrid excitons whose electron- and/or hole-component are delocalized over two or more TMD layers; so far, a detailed characterization of the energy landscape and dynamics of optically dark hybrid excitons is missing. In this work, using femtosecond momentum microscopy, we quantitatively compare the formation dynamics of momentum-forbidden intralayer excitons in monolayer WSe2 with the formation dynamics of momentum-forbidden hybrid excitons in heterobilayer WSe2/MoS2, and draw three key conclusions: First, we find that the energy of hybrid excitons is reduced when compared to excitons with pure intralayer character. Second, in direct comparison with microscopic modelling, we show that the momentum-forbidden intralayer and hybrid excitons are formed via exciton-phonon scattering from optically excited bright excitons. And third, we show that the efficiency for phonon absorption and emission processes in the mono- and the heterobilayer is strongly dependent on the energy alignment of the dark intralayer and hybrid excitons with respect to the optically excited bright exciton.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: Optical excitations, hybrid excitons, charge-transfer processes

刊行年月日: 2023-07-01

出版者: IOP Publishing

掲載誌:

• 2D Materials (ISSN: 20531583) vol. 10 issue. 3 035039

研究助成金:

• saudi arabian ministry for higher education
• Graphene Flagship 881603
• Deutsche Forschungsgemeinschaft 217133147/SFB 1073
• Japan Society for the Promotion of Science 20H00354
• World Premier International Research Center MEXT
• Engineering and Physical Sciences Research Council EP/T001038/1

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.1088/2053-1583/ace067

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更新時刻: 2025-02-25 16:30:36 +0900

MDRでの公開時刻: 2025-02-25 16:30:37 +0900