Large trion binding energy in monolayer WS2 via strain-enhanced electron–phonon coupling

Yunus Waheed; Sumitra Shit; Jithin T. Surendran; Indrajeet D. Prasad; Kenji Watanabe; Takashi Taniguchi; Santosh Kumar

doi:10.1038/s43246-025-00809-z

Journal article Large trion binding energy in monolayer WS2 via strain-enhanced electron–phonon coupling

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Yunus Waheed, Sumitra Shit, Jithin T. Surendran, Indrajeet D. Prasad, Kenji Watanabe, Takashi Taniguchi, Santosh Kumar. Large trion binding energy in monolayer WS2 via strain-enhanced electron–phonon coupling. Communications Materials. 2025, 6 (1), 86. https://doi.org/10.1038/s43246-025-00809-z

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Transition metal dichalcogenides and related layered materials in their monolayer and a few layers thicknesses regime provide a promising optoelectronic platform for exploring the excitonic- and many-body physics. Strain engineering has emerged as a potent technique for tuning the excitonic emission energies favorable for exciton-based devices. We have investigated the effects of nanoparticle-induced local strain on the optical properties of exciton, X0, and trion, X-, in monolayer WS2. The biaxial tensile strain in the range of 0.1 - 2.0 % was quantified and verified by monitoring the changes in three prominent Raman modes of WS2: E12g(Γ), A1g, and 2LA(M). We obtained a remarkable increase of 34meV in X- binding energy with an average tuning rate of 17.5 ± 2.5 meV/% biaxial strain across all the samples irrespective of the surrounding dielectric environment of monolayer WS2 and the sample preparation conditions. At the highest tensile strain of ≈2%, we have achieved the largest binding energy ≈100 meV for X-, leading to its enhanced emission intensity and thermal stability. By investigating strain-induced linewidth broadening and deformation potentials of both X0 and X- emission, we elucidate that the increase in X- binding energy is due to strain-enhanced electron-phonon coupling. This work holds relevance for future X--based nano-opto-electro-mechanical systems and devices.

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