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Title

Strain Control of Exciton–Phonon Coupling in Atomically Thin Semiconductors

AuthorsNiehues, Iris; Castellanos-Gómez, Andrés ; Bratschitsch, Rudolf
KeywordsExcitons
Exciton−phonon coupling
Line width
Strain
Transition metal dichalcogenide
Issue Date1-Feb-2018
PublisherAmerican Chemical Society
CitationNano Letters 18(3): 1751-1757 (2018)
AbstractSemiconducting transition metal dichalcogenide (TMDC) monolayers have exceptional physical properties. They show bright photoluminescence due to their unique band structure and absorb more than 10% of the light at their excitonic resonances despite their atomic thickness. At room temperature, the width of the exciton transitions is governed by the exciton–phonon interaction leading to strongly asymmetric line shapes. TMDC monolayers are also extremely flexible, sustaining mechanical strain of about 10% without breaking. The excitonic properties strongly depend on strain. For example, exciton energies of TMDC monolayers significantly redshift under uniaxial tensile strain. Here, we demonstrate that the width and the asymmetric line shape of excitonic resonances in TMDC monolayers can be controlled with applied strain. We measure photoluminescence and absorption spectra of the A exciton in monolayer MoSe2, WSe2, WS2, and MoS2 under uniaxial tensile strain. We find that the A exciton substantially narrows and becomes more symmetric for the selenium-based monolayer materials, while no change is observed for atomically thin WS2. For MoS2 monolayers, the line width increases. These effects are due to a modified exciton–phonon coupling at increasing strain levels because of changes in the electronic band structure of the respective monolayer materials. This interpretation based on steady-state experiments is corroborated by time-resolved photoluminescence measurements. Our results demonstrate that moderate strain values on the order of only 1% are already sufficient to globally tune the exciton–phonon interaction in TMDC monolayers and hold the promise for controlling the coupling on the nanoscale.
DescriptionNiehues, Iris et al.
Publisher version (URL)http://dx.doi.org/10.1021/acs.nanolett.7b04868
URIhttp://hdl.handle.net/10261/164502
DOI10.1021/acs.nanolett.7b04868
ISSN1530-6984
E-ISSN1530-6992
Appears in Collections:(ICMM) Artículos
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