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Correlated electronic phases in twisted bilayer transition metal dichalcogenides

Nature Materials volume 19, pages 861–866 (2020)Cite this article

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Abstract

In narrow electron bands in which the Coulomb interaction energy becomes comparable to the bandwidth, interactions can drive new quantum phases. Such flat bands in twisted graphene-based systems result in correlated insulator, superconducting and topological states. Here we report evidence of low-energy flat bands in twisted bilayer WSe2, with signatures of collective phases observed over twist angles that range from 4 to 5.1°. At half-band filling, a correlated insulator appeared that is tunable with both twist angle and displacement field. At a 5.1° twist, zero-resistance pockets were observed on doping away from half filling at temperatures below 3 K, which indicates a possible transition to a superconducting state. The observation of tunable collective phases in a simple band, which hosts only two holes per unit cell at full filling, establishes twisted bilayer transition metal dichalcogenides as an ideal platform to study correlated physics in two dimensions on a triangular lattice.

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Fig. 1: Flat bands in twisted bilayer WSe2.
Fig. 2: Displacement-field dependence of vHS for 4.5° tWSe2.
Fig. 3: Angle and displacement-field dependence of the correlated insulator.
Fig. 4: Observation of zero resistance regions around half filling.

Data availability

The data that support the findings of this study are available from the corresponding author upon request.

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Acknowledgements

Studies of the tunable correlated states in the twisted bilayer WSe2 were supported as part of Programmable Quantum Materials, an Energy Frontier Research Center funded by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under award DE-SC0019443. The synthesis of the WSe2 crystals was supported by the NSF MRSEC programme through Columbia in the Center for Precision Assembly of Superstratic and Superatomic Solids (DMR-1420634). The theoretical work was supported by the European Research Council (ERC-2015-AdG694097), cluster of Excellence AIM, SFB925 and Grupos Consolidados (IT1249-19). The Flatiron Institute is a division of the Simons Foundation. We acknowledge support from the Max Planck–New York Center for Non-Equilibrium Quantum Phenomena. We thank F. Wu and L. Fu for helpful discussions. We also thank O. Stapleton, P. Wu and Z. Zheng for help in the device fabrication.

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Author notes

  1. These authors contributed equally: Lei Wang, En-Min Shih and Augusto Ghiotto.

Authors and Affiliations

  1. National Laboratory of Solid-State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China

    Lei Wang

  2. Department of Physics, Columbia University, New York, NY, USA

    Lei Wang, En-Min Shih, Augusto Ghiotto, Abhay N. Pasupathy & Cory R. Dean

  3. Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany

    Lede Xian, Dante M. Kennes & Angel Rubio

  4. Department of Mechanical Engineering, Columbia University, New York, NY, USA

    Daniel A. Rhodes, Cheng Tan, Bumho Kim & James Hone

  5. Department of Electrical Engineering, Columbia University, New York, NY, USA

    Cheng Tan

  6. Center for Computational Quantum Physics, Flatiron Institute, New York, NY, USA

    Martin Claassen & Angel Rubio

  7. Institut für Theorie der Statistischen Physik RWTH Aachen University and JARA-Fundamentals of Future Information Technology, Aachen, Germany

    Dante M. Kennes

  8. Department of Chemistry, Columbia University, New York, NY, USA

    Yusong Bai & Xiaoyang Zhu

  9. National Institute for Materials Science, Tsukuba, Ibaraki, Japan

    Kenji Watanabe & Takashi Taniguchi

  10. Nano-Bio Spectroscopy Group, Departamento de Fisica de Materiales, Universidad del País Vasco, San Sebastian, Spain

    Angel Rubio

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Contributions

L.W., E.-M.S., A.G., C.T. and D.A.R. fabricated the samples. L.W., E.-M.S. and A.G. performed the transport measurements and analysed the data. Y.B. and X.Z. performed the SHG measurements. D.A.R., B.K. and J.H. grew the WSe2 crystals. K.W. and T.T. grew the hBN crystals. L.X. performed the density functional theory and tight-binding calculations. M.C. and D.M.K. did the mean-field calculations. A.R. supervised the theoretical aspects of this work. L.W., E.-M.S., A.G., C.R.D. and A.P. wrote the manuscript with input from all the authors.

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Correspondence to Angel Rubio, Abhay N. Pasupathy or Cory R. Dean.

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Supplementary information

Supplementary theory calculation and Figs. 1–19.

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Wang, L., Shih, EM., Ghiotto, A. et al. Correlated electronic phases in twisted bilayer transition metal dichalcogenides. Nat. Mater. 19, 861–866 (2020). https://doi.org/10.1038/s41563-020-0708-6

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