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Strongly correlated Chern insulators in magic-angle twisted bilayer graphene

Author

Listed:
  • Kevin P. Nuckolls

    (Princeton University)

  • Myungchul Oh

    (Princeton University)

  • Dillon Wong

    (Princeton University)

  • Biao Lian

    (Princeton University)

  • Kenji Watanabe

    (National Institute for Materials Science)

  • Takashi Taniguchi

    (National Institute for Materials Science)

  • B. Andrei Bernevig

    (Princeton University)

  • Ali Yazdani

    (Princeton University)

Abstract

Interactions between electrons and the topology of their energy bands can create unusual quantum phases of matter. Most topological electronic phases appear in systems with weak electron–electron interactions. The instances in which topological phases emerge only as a result of strong interactions are rare and mostly limited to those realized in intense magnetic fields1. The discovery of flat electronic bands with topological character in magic-angle twisted bilayer graphene (MATBG) has created a unique opportunity to search for strongly correlated topological phases2–9. Here we introduce a local spectroscopic technique using a scanning tunnelling microscope to detect a sequence of topological insulators in MATBG with Chern numbers C = ±1, ±2 and ±3, which form near filling factors of ±3, ±2 and ±1 electrons per moiré unit cell, respectively, and are stabilized by modest magnetic fields. One of the phases detected here (C = +1) was previously observed when the sublattice symmetry of MATBG was intentionally broken by a hexagonal boron nitride substrate, with interactions having a secondary role9. We demonstrate that strong electron–electron interactions alone can produce not only the previously observed phase, but also other unexpected Chern insulating phases in MATBG. The full sequence of phases that we observe can be understood by postulating that strong correlations favour breaking time-reversal symmetry to form Chern insulators that are stabilized by weak magnetic fields. Our findings illustrate that many-body correlations can create topological phases in moiré systems beyond those anticipated from weakly interacting models.

Suggested Citation

  • Kevin P. Nuckolls & Myungchul Oh & Dillon Wong & Biao Lian & Kenji Watanabe & Takashi Taniguchi & B. Andrei Bernevig & Ali Yazdani, 2020. "Strongly correlated Chern insulators in magic-angle twisted bilayer graphene," Nature, Nature, vol. 588(7839), pages 610-615, December.
  • Handle: RePEc:nat:nature:v:588:y:2020:i:7839:d:10.1038_s41586-020-3028-8
    DOI: 10.1038/s41586-020-3028-8
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    Citations

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    Cited by:

    1. J. Díez-Mérida & A. Díez-Carlón & S. Y. Yang & Y.-M. Xie & X.-J. Gao & J. Senior & K. Watanabe & T. Taniguchi & X. Lu & A. P. Higginbotham & K. T. Law & Dmitri K. Efetov, 2023. "Symmetry-broken Josephson junctions and superconducting diodes in magic-angle twisted bilayer graphene," Nature Communications, Nature, vol. 14(1), pages 1-7, December.
    2. Ravi Kumar & Saurabh Kumar Srivastav & Ujjal Roy & Jinhong Park & Christian Spånslätt & K. Watanabe & T. Taniguchi & Yuval Gefen & Alexander D. Mirlin & Anindya Das, 2024. "Electrical noise spectroscopy of magnons in a quantum Hall ferromagnet," Nature Communications, Nature, vol. 15(1), pages 1-9, December.
    3. Qiaolu Chen & Zhe Zhang & Haoye Qin & Aleksi Bossart & Yihao Yang & Hongsheng Chen & Romain Fleury, 2024. "Anomalous and Chern topological waves in hyperbolic networks," Nature Communications, Nature, vol. 15(1), pages 1-7, December.
    4. Maine Christos & Subir Sachdev & Mathias S. Scheurer, 2023. "Nodal band-off-diagonal superconductivity in twisted graphene superlattices," Nature Communications, Nature, vol. 14(1), pages 1-11, December.
    5. Saisab Bhowmik & Bhaskar Ghawri & Youngju Park & Dongkyu Lee & Suvronil Datta & Radhika Soni & K. Watanabe & T. Taniguchi & Arindam Ghosh & Jeil Jung & U. Chandni, 2023. "Spin-orbit coupling-enhanced valley ordering of malleable bands in twisted bilayer graphene on WSe2," Nature Communications, Nature, vol. 14(1), pages 1-8, December.
    6. Wenqiang Zhou & Jing Ding & Jiannan Hua & Le Zhang & Kenji Watanabe & Takashi Taniguchi & Wei Zhu & Shuigang Xu, 2024. "Layer-polarized ferromagnetism in rhombohedral multilayer graphene," Nature Communications, Nature, vol. 15(1), pages 1-8, December.
    7. Keshav Singh & Aaron Chew & Jonah Herzog-Arbeitman & B. Andrei Bernevig & Oskar Vafek, 2024. "Topological heavy fermions in magnetic field," Nature Communications, Nature, vol. 15(1), pages 1-12, December.
    8. Canxun Zhang & Tiancong Zhu & Tomohiro Soejima & Salman Kahn & Kenji Watanabe & Takashi Taniguchi & Alex Zettl & Feng Wang & Michael P. Zaletel & Michael F. Crommie, 2023. "Local spectroscopy of a gate-switchable moiré quantum anomalous Hall insulator," Nature Communications, Nature, vol. 14(1), pages 1-7, December.
    9. Pratap Chandra Adak & Subhajit Sinha & Debasmita Giri & Dibya Kanti Mukherjee & Chandan & L. D. Varma Sangani & Surat Layek & Ayshi Mukherjee & Kenji Watanabe & Takashi Taniguchi & H. A. Fertig & Arij, 2022. "Perpendicular electric field drives Chern transitions and layer polarization changes in Hofstadter bands," Nature Communications, Nature, vol. 13(1), pages 1-8, December.
    10. Anushree Datta & M. J. Calderón & A. Camjayi & E. Bascones, 2023. "Heavy quasiparticles and cascades without symmetry breaking in twisted bilayer graphene," Nature Communications, Nature, vol. 14(1), pages 1-8, December.
    11. Le Liu & Shihao Zhang & Yanbang Chu & Cheng Shen & Yuan Huang & Yalong Yuan & Jinpeng Tian & Jian Tang & Yiru Ji & Rong Yang & Kenji Watanabe & Takashi Taniguchi & Dongxia Shi & Jianpeng Liu & Wei Yan, 2022. "Isospin competitions and valley polarized correlated insulators in twisted double bilayer graphene," Nature Communications, Nature, vol. 13(1), pages 1-7, December.
    12. Jesse C. Hoke & Yifan Li & Julian May-Mann & Kenji Watanabe & Takashi Taniguchi & Barry Bradlyn & Taylor L. Hughes & Benjamin E. Feldman, 2024. "Uncovering the spin ordering in magic-angle graphene via edge state equilibration," Nature Communications, Nature, vol. 15(1), pages 1-7, December.
    13. Daniel Shaffer & Jian Wang & Luiz H. Santos, 2022. "Unconventional self-similar Hofstadter superconductivity from repulsive interactions," Nature Communications, Nature, vol. 13(1), pages 1-12, December.
    14. Si-yu Li & Zhengwen Wang & Yucheng Xue & Yingbo Wang & Shihao Zhang & Jianpeng Liu & Zheng Zhu & Kenji Watanabe & Takashi Taniguchi & Hong-jun Gao & Yuhang Jiang & Jinhai Mao, 2022. "Imaging topological and correlated insulating states in twisted monolayer-bilayer graphene," Nature Communications, Nature, vol. 13(1), pages 1-7, December.

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