Article Correlated topological flat bands in rhombohedral graphite

Hongyun Zhang ORCID ; Qian Li ORCID ; Michael G. Scheer ORCID ; Renqi Wang ORCID ; Chuyi Tuo ; Nianlong Zou ; Wanying Chen ; Jiaheng Li ; Xuanxi Cai ORCID ; Changhua Bao ORCID ; Ming-Rui Li ; Ke Deng ORCID ; Kenji Watanabe SAMURAI ORCID ; Takashi Taniguchi SAMURAI ORCID ; Mao Ye ; Peizhe Tang ORCID ; Yong Xu ; Pu Yu ORCID ; Jose Avila ORCID ; Pavel Dudin ORCID ; Jonathan D. Denlinger ORCID ; Hong Yao ; Biao Lian ; Wenhui Duan ORCID ; Shuyun Zhou ORCID

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Hongyun Zhang, Qian Li, Michael G. Scheer, Renqi Wang, Chuyi Tuo, Nianlong Zou, Wanying Chen, Jiaheng Li, Xuanxi Cai, Changhua Bao, Ming-Rui Li, Ke Deng, Kenji Watanabe, Takashi Taniguchi, Mao Ye, Peizhe Tang, Yong Xu, Pu Yu, Jose Avila, Pavel Dudin, Jonathan D. Denlinger, Hong Yao, Biao Lian, Wenhui Duan, Shuyun Zhou. Correlated topological flat bands in rhombohedral graphite. Proceedings of the National Academy of Sciences. 2024, 121 (43), . https://doi.org/10.1073/pnas.2410714121

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(abstract)

Flat bands and non-trivial topological physics are two important topics for condensed matter physics over the past decade. While flat bands can lead to emergent properties such as superconductivity, correlated insulating state etc, non-trivial band topology can give rise to topologically protected surface or edge states. With a unique stacking configuration analogous to the Su-Schrieffer-Heeger (SSH) model, rhombohedral graphite (RG) is a promising candidate for realizing both flat bands and nontrivial topological physics. Here we report experimental evidence of topological flat bands on the surface of bulk RG, which are protected by bulk spiral Dirac nodal lines via the bulk-boundary correspondence. Moreover, upon in situ electron doping, the degeneracy of the flat bands is spontaneously lifted, with an order- of-magnitude increase in the bandwidth of the lower split band. Hartree-Fock calculations support spontaneous flavor symmetry breaking under doping but fail to explain other observations such as the pinning of flat bands near the Fermi level, which suggests that correlation effects beyond mean-field theory are important in this system. Our work establishes RG as a spiral Dirac nodal line semimetal with topological surface flat bands and exotic correlation effects, providing a new platform for investigating the rich interplay between nontrivial band topology and interaction-driven symmetry-broken states.

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Keyword: Flat bands, topological physics, rhombohedral graphite

Date published: 2024-10-22

Publisher: Proceedings of the National Academy of Sciences

Journal:

  • Proceedings of the National Academy of Sciences (ISSN: 00278424) vol. 121 issue. 43

Funding:

  • The National Natural Science Foundation of China 12234011
  • The National Key&D Program of China 2021YFA1400100
  • The National Natural Science Foundation of China 52388201
  • National Science Foundation through Princeton University's Materials Research Science and Engineering Center DMR-2011750
  • The National Natural Science Foundation of China 52025024
  • China Postdoctoral Science Foundation 2022M721887
  • National Natural Science Foundation of China 12304226

Manuscript type: Publisher's version (Version of record)

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First published URL: https://doi.org/10.1073/pnas.2410714121

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Updated at: 2025-02-05 12:31:25 +0900

Published on MDR: 2025-02-05 12:31:25 +0900

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