Giant Stark splitting of an exciton in bilayer MoS2

Abstract

Transition metal dichalcogenides (TMDs) constitute a versatile platform for atomically thin optoelectronics devices and spin–valley memory applications. In monolayer TMDs the optical absorption is strong, but the transition energy cannot be tuned as the neutral exciton has essentially no out-of-plane static electric dipole1,2. In contrast, interlayer exciton transitions in heterobilayers are widely tunable in applied electric fields, but their coupling to light is substantially reduced. In this work, we show tuning over 120 meV of interlayer excitons with a high oscillator strength in bilayer MoS2 due to the quantum-confined Stark effect3. We optically probed the interaction between intra- and interlayer excitons as they were energetically tuned into resonance. Interlayer excitons interact strongly with intralayer B excitons, as demonstrated by a clear avoided crossing, whereas the interaction with intralayer A excitons is substantially weaker. Our observations are supported by density functional theory (DFT) calculations, which include excitonic effects. In MoS2 trilayers, our experiments uncovered two types of interlayer excitons with and without in-built electric dipoles. Highly tunable excitonic transitions with large in-built dipoles and oscillator strengths will result in strong exciton–exciton interactions and therefore hold great promise for non-linear optics with polaritons.

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Fig. 1: MoS2 bilayer van der Waals heterostructure (vdWH) in an applied electric field at T = 4 K.
Fig. 2: Electric-field dependence in a magnetic field (Bz = +9 T).
Fig. 3: Beyond DFT calculations of the electric field effects on the band structure and excitonic properties of a 2H MoS2 bilayer.
Fig. 4: MoS2 trilayer in an applied electric field.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

N.L., L.S. and R.J.W. acknowledge funding from the PhD School Quantum Computing and Quantum Technology, SNF (project no. 200020_156637), Swiss Nanoscience Institute and NCCR QSIT. S.S., I.P., C.R., D.L., A.B., X.M., I.C.G. and B.U. acknowledge funding from ANR 2D-vdW-Spin, ANR VallEx, ANR MagicValley, ITN 4PHOTON Marie Sklodowska Curie grant agreement no. 721394 and the Institut Universitaire de France. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan, grant no. JPMXP0112101001, JSPS KAKENHI grant no. JP20H00354 and the CREST(JPMJCR15F3), JST. I.C.G. thanks the CALMIP initiative for the generous allocation of computational time, through the project p0812, as well as GENCI-CINES and GENCI-IDRIS for grant A006096649. We thank J.-M. Poumirol for the atomic force microscopy measurements and J. G. Roch for crucial help at early stages of this work.

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Contributions

T.T. and K.W. grew the high-quality hBN bulk crystal. N.L., S.S., I.P. and C.R. fabricated the encapsulated samples. D.L. designed and built the magneto-optics set-up. N.L., S.S., I.P., L.S. and C.R. performed optical spectroscopy measurements. N.L, L.S., I.P., S.S., C.R., A.B. and X.M. analysed the optical spectra and interpreted the data. I.C.G. performed the DFT GW+BSE calculations. R.J.W. and B.U. suggested the experiments and supervised the project. N.L., I.C.G. and B.U. wrote the manuscript with input from all the authors.

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Correspondence to Bernhard Urbaszek.

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Peer review information Nature Nanotechnology thanks Thomas Volz and the other, anonymous, reviewer for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1–10, Discussion and Tables I and II.

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Leisgang, N., Shree, S., Paradisanos, I. et al. Giant Stark splitting of an exciton in bilayer MoS2. Nat. Nanotechnol. (2020). https://doi.org/10.1038/s41565-020-0750-1

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