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Maximized electron interactions at the magic angle in twisted bilayer graphene

Author

Listed:
  • Alexander Kerelsky

    (Columbia University)

  • Leo J. McGilly

    (Columbia University)

  • Dante M. Kennes

    (Freie Universität Berlin)

  • Lede Xian

    (Max Planck Institute for the Structure and Dynamics of Matter)

  • Matthew Yankowitz

    (Columbia University)

  • Shaowen Chen

    (Columbia University
    Columbia University)

  • K. Watanabe

    (National Institute for Materials Science)

  • T. Taniguchi

    (National Institute for Materials Science)

  • James Hone

    (Columbia University)

  • Cory Dean

    (Columbia University)

  • Angel Rubio

    (Max Planck Institute for the Structure and Dynamics of Matter
    The Flatiron Institute)

  • Abhay N. Pasupathy

    (Columbia University)

Abstract

The electronic properties of heterostructures of atomically thin van der Waals crystals can be modified substantially by moiré superlattice potentials from an interlayer twist between crystals1,2. Moiré tuning of the band structure has led to the recent discovery of superconductivity3,4 and correlated insulating phases5 in twisted bilayer graphene (TBG) near the ‘magic angle’ of twist of about 1.1 degrees, with a phase diagram reminiscent of high-transition-temperature superconductors. Here we directly map the atomic-scale structural and electronic properties of TBG near the magic angle using scanning tunnelling microscopy and spectroscopy. We observe two distinct van Hove singularities (VHSs) in the local density of states around the magic angle, with an energy separation of 57 millielectronvolts that drops to 40 millielectronvolts with high electron/hole doping. Unexpectedly, the VHS energy separation continues to decrease with decreasing twist angle, with a lowest value of 7 to 13 millielectronvolts at a magic angle of 0.79 degrees. More crucial to the correlated behaviour of this material, we find that at the magic angle, the ratio of the Coulomb interaction to the bandwidth of each individual VHS (U/t) is maximized, which is optimal for electronic Cooper pairing mechanisms. When doped near the half-moiré-band filling, a correlation-induced gap splits the conduction VHS with a maximum size of 6.5 millielectronvolts at 1.15 degrees, dropping to 4 millielectronvolts at 0.79 degrees. We capture the doping-dependent and angle-dependent spectroscopy results using a Hartree–Fock model, which allows us to extract the on-site and nearest-neighbour Coulomb interactions. This analysis yields a U/t of order unity indicating that magic-angle TBG is moderately correlated. In addition, scanning tunnelling spectroscopy maps reveal an energy- and doping-dependent three-fold rotational-symmetry breaking of the local density of states in TBG, with the strongest symmetry breaking near the Fermi level and further enhanced when doped to the correlated gap regime. This indicates the presence of a strong electronic nematic susceptibility or even nematic order in TBG in regions of the phase diagram where superconductivity is observed.

Suggested Citation

  • Alexander Kerelsky & Leo J. McGilly & Dante M. Kennes & Lede Xian & Matthew Yankowitz & Shaowen Chen & K. Watanabe & T. Taniguchi & James Hone & Cory Dean & Angel Rubio & Abhay N. Pasupathy, 2019. "Maximized electron interactions at the magic angle in twisted bilayer graphene," Nature, Nature, vol. 572(7767), pages 95-100, August.
  • Handle: RePEc:nat:nature:v:572:y:2019:i:7767:d:10.1038_s41586-019-1431-9
    DOI: 10.1038/s41586-019-1431-9
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    Citations

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    Cited by:

    1. 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.
    2. Sunny Gupta & Henry Yu & Boris I. Yakobson, 2022. "Designing 1D correlated-electron states by non-Euclidean topography of 2D monolayers," Nature Communications, Nature, vol. 13(1), pages 1-6, December.
    3. 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.
    4. 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.
    5. Dongfei Wang & De-Liang Bao & Qi Zheng & Chang-Tian Wang & Shiyong Wang & Peng Fan & Shantanu Mishra & Lei Tao & Yao Xiao & Li Huang & Xinliang Feng & Klaus Müllen & Yu-Yang Zhang & Roman Fasel & Pasc, 2023. "Twisted bilayer zigzag-graphene nanoribbon junctions with tunable edge states," Nature Communications, Nature, vol. 14(1), pages 1-9, December.
    6. J. González & T. Stauber, 2023. "Ising superconductivity induced from spin-selective valley symmetry breaking in twisted trilayer graphene," Nature Communications, Nature, vol. 14(1), pages 1-7, December.
    7. 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.
    8. 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.
    9. 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.
    10. 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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