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Published September 22, 2021 | Supplemental Material
Journal Article Open

Refractive Index Modulation in Monolayer Molybdenum Diselenide


Two-dimensional transition metal dichalcogenides are promising candidates for ultrathin light modulators due to their highly tunable excitonic resonances at visible and near-infrared wavelengths. At cryogenic temperatures, large excitonic reflectivity in monolayer molybdenum diselenide (MoSe₂) has been shown, but the permittivity and index modulation have not been studied. Here, we demonstrate large gate-tunability of complex refractive index in monolayer MoSe2 by Fermi level modulation and study the doping dependence of the A and B excitonic resonances for temperatures between 4 and 150 K. By tuning the charge density, we observe both temperature- and carrier-dependent epsilon-near-zero response in the permittivity and transition from metallic to dielectric near the A exciton energy. We attribute the dynamic control of the refractive index to the interplay between radiative and non-radiative decay channels that are tuned upon gating. Our results suggest the potential of monolayer MoSe₂ as an active material for emerging photonics applications.

Additional Information

© 2021 American Chemical Society. Received 4 June 2021. Revised 28 August 2021. Published online 1 September 2021. The authors thank Cora Went, Joeson Wong, and Hamidreza Akbari for fruitful discussions and feedback on the work. The authors gratefully acknowledge support from the U.S. Department of Energy, Office of Science, under grant DE-FG02-07ER46405. C.U.H. acknowledges support from the Swiss National Science Foundation through the Early Postdoc Mobility Fellowship, grant no. P2EZP2_191880. Author Contributions: M.L, S.B., and H.A.A. conceived the project. M.L. fabricated the samples with support from S.B. M.L., S.B., and C.U.H. worked on measurements. M.L. and C.U.H. performed FDTD simulations. M.L. analyzed the data and wrote the manuscript. H.A.A. supervised the project. All authors discussed the implications of the results and provided important feedback. The authors declare no competing financial interest.

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August 22, 2023
October 23, 2023