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Published April 25, 2023 | public
Journal Article

Rydberg Excitons and Trions in Monolayer MoTe₂


Monolayer transition metal dichalcogenide (TMDC) semiconductors exhibit strong excitonic optical resonances, which serve as a microscopic, noninvasive probe into their fundamental properties. Like the hydrogen atom, such excitons can exhibit an entire Rydberg series of resonances. Excitons have been extensively studied in most TMDCs (MoS₂, MoSe₂, WS₂, and WSe₂), but detailed exploration of excitonic phenomena has been lacking in the important TMDC material molybdenum ditelluride (MoTe₂). Here, we report an experimental investigation of excitonic luminescence properties of monolayer MoTe₂ to understand the excitonic Rydberg series, up to 3s. We report a significant modification of emission energies with temperature (4 to 300 K), thereby quantifying the exciton–phonon coupling. Furthermore, we observe a strongly gate-tunable exciton–trion interplay for all the Rydberg states governed mainly by free-carrier screening, Pauli blocking, and band gap renormalization in agreement with the results of first-principles GW plus Bethe–Salpeter equation approach calculations. Our results help bring monolayer MoTe₂ closer to its potential applications in near-infrared optoelectronics and photonic devices.

Additional Information

© 2023 American Chemical Society. The experimental measurements were obtained under support from the US Department of Energy Physical Behavior of Materials program, under grant DE-FG02-07ER46405. The electronic structure calculations for the development of the plasmon–pole model is supported by the US Department of Energy Center for Computational Study of Excited-state Phenomena in Energy Materials (C2SEPEM) - (Many-body perturbation theory calculations) and the Theory of Materials FWP (development of the plasmon-pole model) under contract No. DE-AC02-05CH11231. Computational resources are provided by the National Energy Research Scientific Computing Center (NERSC) and the Texas Advanced Computing Center (TACC) at The University of Texas at Austin, funded by the National Science Foundation (NSF) award 1818253, through allocation DMR21077. A.C. acknowledges the support from Wallonie Bruxelles International. A.V.D. and S.K. acknowledge support through the Material Genome Initiative funding allocated to the National Institute of Standards and Technology. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the Ministry of Education, Culture, Sports, Science and Technology (MEXT grant JPMXP0112101001); Japan Society for the Promotion of Science (JSPS KAKENHI grant JP20H00354); and Centers of Research Excellence in Science and Technology (CREST grant JPMJCR15F3), Japan Science and Technology Agency (JST). The authors thank Eoin Caffrey and Dr. Pin Chieh Wu for their support. D.Y.Q. acknowledges support by a 2021 Packard Fellowship for Science and Engineering from the David and Lucile Packard Foundation. Author Contributions. S.B. and H.A.A conceived the project. S.B. fabricated MoTe2-gated heterostructures and performed characterization, optical measurements, and analysis of the data. J.W., H.A., and Z.Y.A.B. assisted in optical measurements and discussions. A.C. led the MBPT calculations with help from J.B.H. and S.P. and inputs from F.H.J., D.Y.Q., and J.B.N. S.K. and A.V.D. provided MoTe2 crystals, and K.W. and T.T provided hBN crystals. S.B. wrote the manuscript with input from all authors. H.A.A. supervised the project. The authors declare no competing financial interest. Disclaimer: Certain commercial equipment, instruments, or materials are identified in this paper in order to specify the experimental procedure adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the materials or equipment identified are necessarily the best available for the purpose.

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August 22, 2023
October 20, 2023