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Strongly correlated electrons and hybrid excitons in a moiré heterostructure


Two-dimensional materials and their heterostructures constitute a promising platform to study correlated electronic states, as well as the many-body physics of excitons. Transport measurements on twisted graphene bilayers have revealed a plethora of intertwined electronic phases, including Mott insulators, strange metals and superconductors1,2,3,4,5. However, signatures of such strong electronic correlations in optical spectroscopy have hitherto remained unexplored. Here we present experiments showing how excitons that are dynamically screened by itinerant electrons to form exciton-polarons6,7 can be used as a spectroscopic tool to investigate interaction-induced incompressible states of electrons. We study a molybdenum diselenide/hexagonal boron nitride/molybdenum diselenide heterostructure that exhibits a long-period moiré superlattice, as evidenced by coherent hole-tunnelling-mediated avoided crossings of an intralayer exciton with three interlayer exciton resonances separated by about five millielectronvolts. For electron densities corresponding to half-filling of the lowest moiré subband, we observe strong layer pseudospin paramagnetism, demonstrated by an abrupt transfer of all the (roughly 1,500) electrons from one molybdenum diselenide layer to the other on application of a small perpendicular electric field. Remarkably, the electronic state at half-filling of each molybdenum diselenide layer is resilient towards charge redistribution by the applied electric field, demonstrating an incompressible Mott-like state of electrons. Our experiments demonstrate that optical spectroscopy provides a powerful tool for investigating strongly correlated electron physics in the bulk and paves the way for investigating Bose–Fermi mixtures of degenerate electrons and dipolar excitons.

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Fig. 1: Device structure and basic characterization.
Fig. 2: Electric field dependence of PL and differential reflectance at charge neutrality.
Fig. 3: Gate dependence of differential reflectance spectrum of MoSe2/hBN/MoSe2.
Fig. 4: Gate dependence of intralayer exciton resonance in the low-electron-density regime.
Fig. 5: Electric field dependence of differential reflectance spectrum in the low-electron-density regime.

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Data availability

The data that support the findings of this study are available in the ETH Research Collection (


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We acknowledge discussions with E. Demler, R. Schmidt, T. Smolenski, A. Popert and P. Knüppel. This work was supported by the Swiss National Science Foundation (SNSF) under grant number 200021-178909/1 and the European Research Council (ERC) Advanced Investigator Grant (POLTDES). Y.S. acknowledges support from the Japan Society for the Promotion of Science (JSPS) overseas research fellowships. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by MEXT, Japan, A3 Foresight by JSPS and CREST (grant number JPMJCR15F3) and JST.

Author information

Authors and Affiliations



Y.S. and I.S. carried out the measurements. Y.S. designed and fabricated the sample. M.K. helped to prepare the experimental setup. K.W. and T.T. grew the hBN crystal. Y.S. performed DFT calculation. Y.S., I.S. and A.I. wrote the manuscript. A.I. supervised the project.

Corresponding authors

Correspondence to Yuya Shimazaki or Ataç Imamoğlu.

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Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature thanks Wang Yao and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended Data Fig. 1 Optical microscope image of the device.

The border of each flake is highlighted with dashed lines, and the material is indicated in the grey box with the corresponding colour. Gr, graphene.

Extended Data Fig. 2 Effect of twist angle and strain on moiré periodicity.

a, Plot of the relation between twist angle and strain difference which gives same moiré periodicity (λmoiré), shown for λmoiré from 20 to 30 nm. b, Strain difference dependence of moiré periodicity for a fixed twist angle of 0.8°.

Extended Data Fig. 3 Band structure of R-stacked MoSe2/hBN/MoSe2 heterostructure obtained from DFT calculation.

ac, The side and top view of the supercell for \({{\rm{R}}}_{{\rm{h}}}^{{\rm{h}}}\) (a), \({{\rm{R}}}_{{\rm{h}}}^{{\rm{X}}}\) (b) and \({{\rm{R}}}_{{\rm{h}}}^{{\rm{M}}}\) (c) used for the calculation. df, The calculated band structure of R-stacked MoSe2/hBN/MoSe2 for \({{\rm{R}}}_{{\rm{h}}}^{{\rm{h}}}\) (d), \({{\rm{R}}}_{{\rm{h}}}^{{\rm{X}}}\) (e) and \({{\rm{R}}}_{{\rm{h}}}^{{\rm{M}}}\) (f) lattice displacement. The insets show the magnified plot of the valence bands around the γ point.

Extended Data Table 1 DFT calculation results for MoSe2/hBN/MoSe2

Supplementary information

Supplementary Information

This file contains Supplementary Information sections 1–8 including Supplementary Figures 1–10.

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Shimazaki, Y., Schwartz, I., Watanabe, K. et al. Strongly correlated electrons and hybrid excitons in a moiré heterostructure. Nature 580, 472–477 (2020).

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