Strain-dependent exciton diffusion in transition metal dichalcogenides

Monolayers of transition metal dichalcogenides have a remarkable excitonic landscape with deeply bound bright and dark exciton states. Their properties are strongly affected by lattice distortions that can be created in a controlled way via strain. Here, we perform a joint theory-experiment study in...

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Bibliographic Details
Published in:2d materials 2021-01, Vol.8 (1), p.15030
Main Authors: Rosati, Roberto, Brem, Samuel, Perea-Causín, Raül, Schmidt, Robert, Niehues, Iris, Michaelis de Vasconcellos, Steffen, Bratschitsch, Rudolf, Malic, Ermin
Format: Article
Language:English
Subjects:
dark excitons
exciton diffusion
strain
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Summary:Monolayers of transition metal dichalcogenides have a remarkable excitonic landscape with deeply bound bright and dark exciton states. Their properties are strongly affected by lattice distortions that can be created in a controlled way via strain. Here, we perform a joint theory-experiment study investigating exciton diffusion in strained tungsten disulfide (WS2) monolayers. We reveal a non-trivial and non-monotonic influence of strain. Lattice deformations give rise to different energy shifts for bright and dark excitons changing the excitonic landscape, the efficiency of intervalley scattering channels and the weight of single exciton species to the overall exciton diffusion. We predict a minimal diffusion coefficient in unstrained WS2 followed by a steep speed-up by a factor of 3 for tensile biaxial strain at about 0.6% strain-in excellent agreement with our experiments. The obtained microscopic insights on the impact of strain on exciton diffusion are applicable to a broad class of multi-valley 2D materials.
ISSN:2053-1583
2053-1583
DOI:10.1088/2053-1583/abbd51