Dark-Exciton Driven Energy Funneling into Dielectric Inhomogeneities in Two-Dimensional Semiconductors

The optoelectronic and transport properties of two-dimensional transition metal dichalcogenide semiconductors (2D TMDs) are highly susceptible to external perturbation, enabling precise tailoring of material function through postsynthetic modifications. Here, we show that nanoscale inhomogeneities k...

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Bibliographic Details
Published in:Nano letters 2022-04, Vol.22 (7), p.2843-2850
Main Authors: Su, Haowen, Xu, Ding, Cheng, Shan-Wen, Li, Baichang, Liu, Song, Watanabe, Kenji, Taniguchi, Takashi, Berkelbach, Timothy C, Hone, James C, Delor, Milan
Format: Article
Language:English
Subjects:
Microscopy
Physical Phenomena
Semiconductors
Transition Elements
Tungsten
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Summary:The optoelectronic and transport properties of two-dimensional transition metal dichalcogenide semiconductors (2D TMDs) are highly susceptible to external perturbation, enabling precise tailoring of material function through postsynthetic modifications. Here, we show that nanoscale inhomogeneities known as nanobubbles can be used for both strain and, less invasively, dielectric tuning of exciton transport in bilayer tungsten diselenide (WSe2). We use ultrasensitive spatiotemporally resolved optical scattering microscopy to directly image exciton transport, revealing that dielectric nanobubbles are surprisingly efficient at funneling and trapping excitons at room temperature, even though the energies of the bright excitons are negligibly affected. Our observations suggest that exciton funneling in dielectric inhomogeneities is driven by momentum-indirect (dark) excitons whose energies are more sensitive to dielectric perturbations than bright excitons. These results reveal a new pathway to control exciton transport in 2D semiconductors with exceptional spatial and energetic precision using dielectric engineering of dark state energetic landscapes.
ISSN:1530-6984
1530-6992
DOI:10.1021/acs.nanolett.1c04997