Abstract
While most approaches to polariton research focus on achieving strong coupling between excitons in monolayer transition metal dichalcogenides (TMDCs) and external microcavities, bulk TMDCs have been largely overlooked due to their reduced exciton oscillator strength and indirect bandgap nature. Here, we report the observation of polariton condensation within the indirect-transition range, enabled by a condensation mechanism in 50-nm-thick WS₂-based bound state in the continuum (BIC) cavities. Our photonic-like BIC polaritons exhibit a significant Rabi splitting energy ( ~ 294 meV) and clear evidence of condensation driven by a mechanism involving indirect excitons that directly inject photons into BIC polaritons. Remarkably, the interaction-induced confinement of polariton condensates can be optically tuned by adjusting the pump laser size, despite a minimal exciton fraction of 6%, distinguishing this system from purely photonic counterparts. These findings open new avenues for exploring polariton physics with indirect excitons in TMDCs and other emerging materials.
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The data supporting the findings of this study, including all source data for the main figures, have been deposited in Figshare and are publicly available at the following link: https://doi.org/10.6084/m9.figshare.30655754.
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Acknowledgements
J.R. acknowledges the POSCO-POSTECH-RIST Convergence Research Center program funded by POSCO, and the National Research Foundation (NRF) grant (RS-2024-00356928) funded by the Ministry of Science and ICT (MSIT) of the Korean government. J.K. acknowledges the Asan Foundation Biomedical Science fellowship and the Presidential Science fellowship funded by the MSIT of the Korean government. M.J. acknowledges the Hyundai Motor Chung Mong-Koo fellowship. S.-H.G. acknowledges support from the NRF grant (RS-2024-00335222) funded by the MSIT of Korea government, and Samsung Science and Technology Foundation (SSTF-BA1902-03). H.G.S. acknowledges support from the NRF grant (RS-2024-00337279 and RS-2024-00454894) funded by the MSIT of Korea government and KIST Institutional Programs (2E33831).
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J.R., S.-H.G., and H.G.S. conceptualized and supervised the study. J.S. and J.K. performed all data analysis and visualization. J.K., M.J., J.L., and S.K. fabricated the sample structures. J.S., H.S.L., D.-J.S., and D.C. conducted the optical experiments and data collection. J.S. and J.K. wrote the original draft. J.R., S.-H.G., and H.G.S. reviewed and edited the final manuscript.
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Sung, J., Kim, J., Lee, H.S. et al. Polariton condensate far-detuned from exciton resonance in WS2 bound states in the continuum. Nat Commun (2025). https://doi.org/10.1038/s41467-025-67454-5
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DOI: https://doi.org/10.1038/s41467-025-67454-5
