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Cascade of phase transitions and Dirac revivals in magic-angle graphene

Author

Listed:
  • U. Zondiner

    (Weizmann Institute of Science)

  • A. Rozen

    (Weizmann Institute of Science)

  • D. Rodan-Legrain

    (Massachusetts Institute of Technology)

  • Y. Cao

    (Massachusetts Institute of Technology)

  • R. Queiroz

    (Weizmann Institute of Science)

  • T. Taniguchi

    (National Institute for Materials Science)

  • K. Watanabe

    (National Institute for Materials Science)

  • Y. Oreg

    (Weizmann Institute of Science)

  • F. Oppen

    (Freie Universität Berlin)

  • Ady Stern

    (Weizmann Institute of Science)

  • E. Berg

    (Weizmann Institute of Science)

  • P. Jarillo-Herrero

    (Massachusetts Institute of Technology)

  • S. Ilani

    (Weizmann Institute of Science)

Abstract

Twisted bilayer graphene near the magic angle1–4 exhibits rich electron-correlation physics, displaying insulating3–6, magnetic7,8 and superconducting phases4–6. The electronic bands of this system were predicted1,2 to narrow markedly9,10 near the magic angle, leading to a variety of possible symmetry-breaking ground states11–17. Here, using measurements of the local electronic compressibility, we show that these correlated phases originate from a high-energy state with an unusual sequence of band population. As carriers are added to the system, the four electronic ‘flavours’, which correspond to the spin and valley degrees of freedom, are not filled equally. Rather, they are populated through a sequence of sharp phase transitions, which appear as strong asymmetric jumps of the electronic compressibility near integer fillings of the moiré lattice. At each transition, a single spin/valley flavour takes all the carriers from its partially filled peers, ‘resetting’ them to the vicinity of the charge neutrality point. As a result, the Dirac-like character observed near charge neutrality reappears after each integer filling. Measurement of the in-plane magnetic field dependence of the chemical potential near filling factor one reveals a large spontaneous magnetization, further substantiating this picture of a cascade of symmetry breaking. The sequence of phase transitions and Dirac revivals is observed at temperatures well above the onset of the superconducting and correlated insulating states. This indicates that the state that we report here, with its strongly broken electronic flavour symmetry and revived Dirac-like electronic character, is important in the physics of magic-angle graphene, forming the parent state out of which the more fragile superconducting and correlated insulating ground states emerge.

Suggested Citation

  • U. Zondiner & A. Rozen & D. Rodan-Legrain & Y. Cao & R. Queiroz & T. Taniguchi & K. Watanabe & Y. Oreg & F. Oppen & Ady Stern & E. Berg & P. Jarillo-Herrero & S. Ilani, 2020. "Cascade of phase transitions and Dirac revivals in magic-angle graphene," Nature, Nature, vol. 582(7811), pages 203-208, June.
  • Handle: RePEc:nat:nature:v:582:y:2020:i:7811:d:10.1038_s41586-020-2373-y
    DOI: 10.1038/s41586-020-2373-y
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    Cited by:

    1. Lan, Yuncheng & Zhao, Xudong & Zhang, Wei & Mu, Lianbo & Wang, Suilin, 2022. "Investigation of the waste heat recovery and pollutant emission reduction potential in graphitization furnace," Energy, Elsevier, vol. 245(C).
    2. Jiachen Yu & Benjamin A. Foutty & Yves H. Kwan & Mark E. Barber & Kenji Watanabe & Takashi Taniguchi & Zhi-Xun Shen & Siddharth A. Parameswaran & Benjamin E. Feldman, 2023. "Spin skyrmion gaps as signatures of strong-coupling insulators in magic-angle twisted bilayer graphene," Nature Communications, Nature, vol. 14(1), pages 1-7, 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. 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.
    5. 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.
    6. 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.
    7. 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.
    8. 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.
    9. 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.
    10. Bhaskar Ghawri & Phanibhusan S. Mahapatra & Manjari Garg & Shinjan Mandal & Saisab Bhowmik & Aditya Jayaraman & Radhika Soni & Kenji Watanabe & Takashi Taniguchi & H. R. Krishnamurthy & Manish Jain & , 2022. "Breakdown of semiclassical description of thermoelectricity in near-magic angle twisted bilayer graphene," Nature Communications, Nature, vol. 13(1), pages 1-7, December.
    11. Hao Chen & Arpit Arora & Justin C. W. Song & Kian Ping Loh, 2023. "Gate-tunable anomalous Hall effect in Bernal tetralayer graphene," Nature Communications, Nature, vol. 14(1), pages 1-6, December.
    12. Daniel Kaplan & Tobias Holder & Binghai Yan, 2023. "General nonlinear Hall current in magnetic insulators beyond the quantum anomalous Hall effect," Nature Communications, Nature, vol. 14(1), pages 1-7, December.
    13. Shubhayu Chatterjee & Taige Wang & Erez Berg & Michael P. Zaletel, 2022. "Inter-valley coherent order and isospin fluctuation mediated superconductivity in rhombohedral trilayer graphene," Nature Communications, Nature, vol. 13(1), pages 1-10, 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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