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Probing momentum-indirect excitons by near-resonance photoluminescence excitation spectroscopy in WS2 monolayer

Probing momentum-indirect excitons by near-resonance photoluminescence excitation spectroscopy in... Coulomb-bound electron-hole pairs (excitons) dominate the optical response of atomically-thin transition metal dichalcogenides (TMDs) semiconductors. The photoluminescence spectrum in W-based TMDs monolayers (i.e. WS2 and WSe2) at low temperature exhibits much richer features than Mo-based TMDs monolayers, whose origin is currently not well understood. Herein, by using near-resonant photoluminescence excitation spectroscopy, we probe the scattering events between excitons and phonons with large -momentum, which provides strong evidence for the momentum-indirect nature of the optical bandgap in monolayer WS2. The scattering between carriers and zone-edge phonons creates excitons at different valleys, among which, the lowest-energy is momentum-indirect. Our findings highlight that more efforts are required to solve the current debate on the inherent bandgap nature of TMD monolayers and the complex photoluminescence spectrum reported on W-based compounds. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png 2D Materials IOP Publishing

Probing momentum-indirect excitons by near-resonance photoluminescence excitation spectroscopy in WS2 monolayer

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Copyright
Copyright © 2020 The Author(s). Published by IOP Publishing Ltd
eISSN
2053-1583
DOI
10.1088/2053-1583/ab817a
Publisher site
See Article on Publisher Site

Abstract

Coulomb-bound electron-hole pairs (excitons) dominate the optical response of atomically-thin transition metal dichalcogenides (TMDs) semiconductors. The photoluminescence spectrum in W-based TMDs monolayers (i.e. WS2 and WSe2) at low temperature exhibits much richer features than Mo-based TMDs monolayers, whose origin is currently not well understood. Herein, by using near-resonant photoluminescence excitation spectroscopy, we probe the scattering events between excitons and phonons with large -momentum, which provides strong evidence for the momentum-indirect nature of the optical bandgap in monolayer WS2. The scattering between carriers and zone-edge phonons creates excitons at different valleys, among which, the lowest-energy is momentum-indirect. Our findings highlight that more efforts are required to solve the current debate on the inherent bandgap nature of TMD monolayers and the complex photoluminescence spectrum reported on W-based compounds.

Journal

2D MaterialsIOP Publishing

Published: Jul 1, 2020

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