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Electronic correlations in twisted bilayer graphene near the magic angle

Nature Physics volume 15, pages 1174–1180 (2019)Cite this article

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An Author Correction to this article was published on 25 October 2019

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Abstract

Twisted bilayer graphene with a twist angle of around 1.1° features a pair of isolated flat electronic bands and forms a platform for investigating strongly correlated electrons. Here, we use scanning tunnelling microscopy to probe the local properties of highly tunable twisted bilayer graphene devices and show that the flat bands deform when aligned with the Fermi level. When the bands are half-filled, we observe the development of gaps originating from correlated insulating states. Near charge neutrality, we find a previously unidentified correlated regime featuring an enhanced splitting of the flat bands. We describe this within a microscopic model that predicts a strong tendency towards nematic ordering. Our results provide insights into symmetry-breaking correlation effects and highlight the importance of electronic interactions for all filling fractions in twisted bilayer graphene.

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Fig. 1: Twisted bilayer graphene.
Fig. 2: Evolution of the TBG point spectrum with back-gate voltage.
Fig. 3: Model calculations and breaking of C3 symmetry.
Fig. 4: Spectroscopy at half-filling of the flat bands.

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Data availability

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

Code availability

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

Change history

  • 25 October 2019

    An amendment to this paper has been published and can be accessed via a link at the top of the paper.

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Acknowledgements

We gratefully acknowledge discussions with R. C. Ashoori, P. Jarillo-Herrero, A. Vishwanath, J. Eisenstein, A. Young and H. Beidenkopf. The STM work is in part supported by NSF DMR-1744011. Sample fabrication efforts are supported by the NSF through program NSF CAREER DMR-1753306. S.N.-P. acknowledges support from a KNI-Weathley fellowship. J.A., G.R., F.v.O., S.N.-P. and H.R. acknowledge the support of IQIM (NSF funded physics frontiers center). J.K. acknowledges support from the Deutsche Forschungsgemeinschaft (DFG 406557161), Y.C. a Kwanjeong fellowship, F.v.O. DFG support through CRC 183, and J.A. support from the Army Research Office under grant award W911NF-17-1-0323 and the NSF through grant DMR-1723367. Y.P., A.T. and J.A. are grateful for support from the Walter Burke Institute for Theoretical Physics at Caltech.

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Authors and Affiliations

  1. T. J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, CA, USA

    Youngjoon Choi, Jeannette Kemmer, Harpreet Arora, Robert Polski, Yiran Zhang, Hechen Ren & Stevan Nadj-Perge

  2. Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA, USA

    Youngjoon Choi, Jeannette Kemmer, Yang Peng, Alex Thomson, Harpreet Arora, Robert Polski, Yiran Zhang, Hechen Ren, Jason Alicea, Gil Refael, Felix von Oppen & Stevan Nadj-Perge

  3. Department of Physics, California Institute of Technology, Pasadena, CA, USA

    Youngjoon Choi, Yang Peng, Alex Thomson, Yiran Zhang, Jason Alicea & Gil Refael

  4. Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, CA, USA

    Yang Peng, Alex Thomson, Jason Alicea & Gil Refael

  5. Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, Berlin, Germany

    Felix von Oppen

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

    Kenji Watanabe & Takashi Taniguchi

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Contributions

Y.C., J.K. and S.N.-P. conceived the experiment. Y.C. and J.K. performed the measurements. Y.C. made the samples with the help of H.A., R.P. and Y.Z. Y.C., J.K., H.R. and S.N.-P. performed data analysis. Y.P. and A.T. developed the theory guided by F.v.O., J.A. and G.R. Y.C., J.K. and S.N.-P. wrote the manuscript with input from all authors.

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Correspondence to Stevan Nadj-Perge.

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Supplementary Information

Additional technical and theoretical details, Supplementary Figs. 1–14, Table 1 and refs. 1–16.

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Choi, Y., Kemmer, J., Peng, Y. et al. Electronic correlations in twisted bilayer graphene near the magic angle. Nat. Phys. 15, 1174–1180 (2019). https://doi.org/10.1038/s41567-019-0606-5

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