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Ambipolar Landau levels and strong band-selective carrier interactions in monolayer WSe2

Abstract

Monolayers (MLs) of transition-metal dichalcogenides (TMDs) exhibit unusual electrical behaviour under magnetic fields due to their intrinsic spin–orbit coupling and lack of inversion symmetry1,2,3,4,5,6,7,8,9,10,11,12,13,14,15. Although recent experiments have also identified the critical role of carrier interactions within these materials11,15, a complete mapping of the ambipolar Landau level (LL) sequence has remained elusive. Here we use single-electron transistors (SETs)16,17 to perform LL spectroscopy in ML WSe2, and provide a comprehensive picture of the electronic structure of a ML TMD for both electrons and holes. We find that the LLs differ notably between the two bands, and follow a unique sequence in the valence band (VB) that is dominated by strong Zeeman effects. The Zeeman splitting in the VB is several times higher than the cyclotron energy, far exceeding the predictions of a single-particle model and, moreover, tunes significantly with doping15. This implies exceptionally strong many-body interactions, and suggests that ML WSe2 can serve as a host for new correlated-electron phenomena.

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Fig. 1: ML WSe2 in the quantum Hall regime.
Fig. 2: Probing scheme and ambipolar LL dispersion.
Fig. 3: Isospin polarization of LLs.
Fig. 4: Density-dependent LL energy gaps in the VB.
Fig. 5: Extracted parameters and effects of interactions.

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Acknowledgements

We thank K. F. Mak, A. Young, B. Feldman and M. Goerbig for valuable technical and theoretical discussions. C.R.D. and J.H. acknowledge support from the US Department of Energy, DE-SC0016703. C.R.D. acknowledges partial support from the David and Lucille Packard foundation. Sample fabrication and materials synthesis was supported by the NSF MRSEC program through Columbia in the Center for Precision Assembly of Superstratic and Superatomic Solids (DMR-1420634). K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan, and JSPS KAKENHI grant no. JP15K21722. A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement no. DMR-0654118, the State of Florida and the US Department of Energy.

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M.V.G. and M.Y. performed the experiments and analysed the data. M.Y., M.V.G. and C.R.D. developed the model of the system and wrote the paper. M.Y., M.V.G. and C.F. fabricated the samples. D.R. grew and characterized the single-crystal WSe2, and K.W. and T.T. grew the single-crystal hBN. J.H., X.Z. and C.R.D. advised on the experiments and data analysis, and contributed to the manuscript writing.

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Correspondence to Cory R. Dean.

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Supplementary text, Figures S1–S8, 4 references

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Gustafsson, M.V., Yankowitz, M., Forsythe, C. et al. Ambipolar Landau levels and strong band-selective carrier interactions in monolayer WSe2. Nature Mater 17, 411–415 (2018). https://doi.org/10.1038/s41563-018-0036-2

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  • DOI: https://doi.org/10.1038/s41563-018-0036-2

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