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Half- and quarter-metals in rhombohedral trilayer graphene

Author

Listed:
  • Haoxin Zhou

    (University of California)

  • Tian Xie

    (University of California)

  • Areg Ghazaryan

    (Institute of Science and Technology)

  • Tobias Holder

    (Weizmann Institute of Science)

  • James R. Ehrets

    (University of California)

  • Eric M. Spanton

    (University of California)

  • Takashi Taniguchi

    (National Institute for Materials Science)

  • Kenji Watanabe

    (National Institute for Materials Science)

  • Erez Berg

    (Weizmann Institute of Science)

  • Maksym Serbyn

    (Institute of Science and Technology)

  • Andrea F. Young

    (University of California)

Abstract

Ferromagnetism is most common in transition metal compounds where electrons occupy highly localized d orbitals. However, ferromagnetic order may also arise in low-density two-dimensional electron systems1–5. Here we show that gate-tuned van Hove singularities in rhombohedral trilayer graphene6 drive spontaneous ferromagnetic polarization of the electron system into one or more spin and valley flavours. Using capacitance and transport measurements, we observe a cascade of transitions tuned to the density and electronic displacement field between phases in which quantum oscillations have fourfold, twofold or onefold degeneracy, associated with a spin- and valley-degenerate normal metal, spin-polarized ‘half-metal’, and spin- and valley-polarized ‘quarter-metal’, respectively. For electron doping, the salient features of the data are well captured by a phenomenological Stoner model7 that includes valley-anisotropic interactions. For hole filling, we observe a richer phase diagram featuring a delicate interplay of broken symmetries and transitions in the Fermi surface topology. Finally, we introduce a moiré superlattice using a rotationally aligned hexagonal boron nitride substrate5,8. Remarkably, we find that the isospin order is only weakly perturbed, with the moiré potential catalysing the formation of topologically nontrivial gapped states whenever itinerant half- or quarter-metal states occur at half- or quarter-superlattice band filling. Our results show that rhombohedral graphene is an ideal platform for well-controlled tests of many-body theory, and reveal magnetism in moiré materials4,5,9,10 to be fundamentally itinerant in nature.

Suggested Citation

  • Haoxin Zhou & Tian Xie & Areg Ghazaryan & Tobias Holder & James R. Ehrets & Eric M. Spanton & Takashi Taniguchi & Kenji Watanabe & Erez Berg & Maksym Serbyn & Andrea F. Young, 2021. "Half- and quarter-metals in rhombohedral trilayer graphene," Nature, Nature, vol. 598(7881), pages 429-433, October.
  • Handle: RePEc:nat:nature:v:598:y:2021:i:7881:d:10.1038_s41586-021-03938-w
    DOI: 10.1038/s41586-021-03938-w
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    Citations

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    Cited by:

    1. Anna M. Seiler & Nils Jacobsen & Martin Statz & Noelia Fernandez & Francesca Falorsi & Kenji Watanabe & Takashi Taniguchi & Zhiyu Dong & Leonid S. Levitov & R. Thomas Weitz, 2024. "Probing the tunable multi-cone band structure in Bernal bilayer graphene," Nature Communications, Nature, vol. 15(1), pages 1-9, December.
    2. 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.
    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. Xiaozhou Zan & Xiangdong Guo & Aolin Deng & Zhiheng Huang & Le Liu & Fanfan Wu & Yalong Yuan & Jiaojiao Zhao & Yalin Peng & Lu Li & Yangkun Zhang & Xiuzhen Li & Jundong Zhu & Jingwei Dong & Dongxia Sh, 2024. "Electron/infrared-phonon coupling in ABC trilayer graphene," Nature Communications, Nature, vol. 15(1), pages 1-6, 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. Jonas B. Profe & Dante M. Kennes, 2022. "TU $$^2$$ 2 FRG: a scalable approach for truncated unity functional renormalization group in generic fermionic models," The European Physical Journal B: Condensed Matter and Complex Systems, Springer;EDP Sciences, vol. 95(3), pages 1-13, March.

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