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Fractional Chern insulators in magic-angle twisted bilayer graphene

Author

Listed:
  • Yonglong Xie

    (Harvard University
    Massachusetts Institute of Technology)

  • Andrew T. Pierce

    (Harvard University)

  • Jeong Min Park

    (Massachusetts Institute of Technology)

  • Daniel E. Parker

    (Harvard University)

  • Eslam Khalaf

    (Harvard University)

  • Patrick Ledwith

    (Harvard University)

  • Yuan Cao

    (Massachusetts Institute of Technology)

  • Seung Hwan Lee

    (Harvard University)

  • Shaowen Chen

    (Harvard University)

  • Patrick R. Forrester

    (Harvard University)

  • Kenji Watanabe

    (National Institute for Material Science)

  • Takashi Taniguchi

    (National Institute for Material Science)

  • Ashvin Vishwanath

    (Harvard University)

  • Pablo Jarillo-Herrero

    (Massachusetts Institute of Technology)

  • Amir Yacoby

    (Harvard University)

Abstract

Fractional Chern insulators (FCIs) are lattice analogues of fractional quantum Hall states that may provide a new avenue towards manipulating non-Abelian excitations. Early theoretical studies1–7 have predicted their existence in systems with flat Chern bands and highlighted the critical role of a particular quantum geometry. However, FCI states have been observed only in Bernal-stacked bilayer graphene (BLG) aligned with hexagonal boron nitride (hBN)8, in which a very large magnetic field is responsible for the existence of the Chern bands, precluding the realization of FCIs at zero field. By contrast, magic-angle twisted BLG9–12 supports flat Chern bands at zero magnetic field13–17, and therefore offers a promising route towards stabilizing zero-field FCIs. Here we report the observation of eight FCI states at low magnetic field in magic-angle twisted BLG enabled by high-resolution local compressibility measurements. The first of these states emerge at 5 T, and their appearance is accompanied by the simultaneous disappearance of nearby topologically trivial charge density wave states. We demonstrate that, unlike the case of the BLG/hBN platform, the principal role of the weak magnetic field is merely to redistribute the Berry curvature of the native Chern bands and thereby realize a quantum geometry favourable for the emergence of FCIs. Our findings strongly suggest that FCIs may be realized at zero magnetic field and pave the way for the exploration and manipulation of anyonic excitations in flat moiré Chern bands.

Suggested Citation

  • Yonglong Xie & Andrew T. Pierce & Jeong Min Park & Daniel E. Parker & Eslam Khalaf & Patrick Ledwith & Yuan Cao & Seung Hwan Lee & Shaowen Chen & Patrick R. Forrester & Kenji Watanabe & Takashi Tanigu, 2021. "Fractional Chern insulators in magic-angle twisted bilayer graphene," Nature, Nature, vol. 600(7889), pages 439-443, December.
    • Handle: RePEc:nat:nature:v:600:y:2021:i:7889:d:10.1038_s41586-021-04002-3
    DOI: 10.1038/s41586-021-04002-3
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    Citations

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    Cited by:

    1. Manabendra Kuiri & Christopher Coleman & Zhenxiang Gao & Aswin Vishnuradhan & Kenji Watanabe & Takashi Taniguchi & Jihang Zhu & Allan H. MacDonald & Joshua Folk, 2022. "Spontaneous time-reversal symmetry breaking in twisted double bilayer graphene," Nature Communications, Nature, vol. 13(1), pages 1-6, December.
    2. 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.
    3. 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.
    4. Lebing Chen & Xiaokun Teng & Hengxin Tan & Barry L. Winn & Garrett E. Granroth & Feng Ye & D. H. Yu & R. A. Mole & Bin Gao & Binghai Yan & Ming Yi & Pengcheng Dai, 2024. "Competing itinerant and local spin interactions in kagome metal FeGe," Nature Communications, Nature, vol. 15(1), pages 1-10, December.
    5. Dorri Halbertal & Simon Turkel & Christopher J. Ciccarino & Jonas B. Profe & Nathan Finney & Valerie Hsieh & Kenji Watanabe & Takashi Taniguchi & James Hone & Cory Dean & Prineha Narang & Abhay N. Pas, 2022. "Unconventional non-local relaxation dynamics in a twisted trilayer graphene moiré superlattice," Nature Communications, Nature, vol. 13(1), pages 1-8, December.
    6. 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.
    7. 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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