Brightening of dark excitons in WS2 via tensile strain-induced excitonic valley convergence

Chowdhury, T and Chatterjee, S and Das, D and Timokhin, I and Núñez, PD and Gokul, AM and Chatterjee, S and Majumdar, K and Ghosh, P and Mishchenko, A and Rahman, A (2024) Brightening of dark excitons in WS2 via tensile strain-induced excitonic valley convergence. In: Physical Review B, 110 (8).

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Abstract

Transition-metal dichalcogenides (TMDs) host tightly bound electron-hole pairs - excitons - which can be either optically bright or dark based on spin and momentum selection rules. In tungsten-based TMDs, a momentum-forbidden dark exciton is the energy ground state, and therefore, it strongly affects the emission properties. In this work, we brighten the momentum-forbidden dark exciton by placing monolayer tungsten disulfide on top of nanotextured substrates, which imparts tensile strain, modifying its electronic band structure. This enables phonon-assisted exciton scattering between momentum valleys, thereby brightening momentum-forbidden dark excitons. In addition to offering a tuning knob for light-matter interactions in two-dimensional materials, our results pave the way for designing ultrasensitive strain-sensing devices based on TMDs. © 2024 American Physical Society.

Item Type:	Journal Article
Publication:	Physical Review B
Publisher:	American Physical Society
Additional Information:	The copyright for this article belongs to the publisher.
Keywords:	Excited states; Excitons; Germanium compounds; Indium phosphide; Layered semiconductors; Phonon scattering; Photons; Tungsten compounds; Wide band gap semiconductors, Bound electrons; Dark excitons; Electron hole pairs; Emission properties; Energy; Excitonics; Selection Rules; Strain induced; Transition metal dichalcogenides (TMD); Tungsten disulfide, Tensile strain
Department/Centre:	Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited:	29 Aug 2024 06:25
Last Modified:	29 Aug 2024 06:25
URI:	http://eprints.iisc.ac.in/id/eprint/85966

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