Correlated topological flat bands in rhombohedral graphite

• 成果类型: Article
• 署名作者: Zhang, Hongyun; Li, Qian; Scheer, Michael G.; Wang, Renqi; Tuo, Chuyi; Zou, Nianlong; Chen, Wanying; Li, Jiaheng; Cai, Xuanxi; Bao, Changhua; Li, Ming-Rui; Deng, Ke; Watanabe, Kenji; Taniguchi, Takashi; Ye, Mao; Tang, Peizhe; Xu, Yong; Yu, Pu; Avila, Jose; Dudin, Pavel; Denlinger, Jonathan D.; Yao, Hong; Lian, Biao; Duan, Wenhui; Zhou, Shuyun
• 署名单位: Tsinghua University; Tsinghua University; Princeton University; Tsinghua University; National Institute for Materials Science; National Institute for Materials Science; Chinese Academy of Sciences; Shanghai Advanced Research Institute, CAS; Beihang University; Max Planck Society; SOLEIL Synchrotron; United States Department of Energy (DOE); Lawrence Berkeley National Laboratory
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-15341
• DOI: 10.1073/pnas.2410714121
• 发表日期: 2024-10-16
• 关键词: trilayer graphene; chern insulator; wave-functions; transitions; semimetal; gap

摘要

Flat bands and nontrivial topological physics are two important topics of condensed matter physics. With a unique stacking configuration analogous to the Su-Schrieffer- Heeger model, rhombohedral graphite (RG) is a potential candidate for realizing both flat bands and nontrivial topological physics. Here, we report experimental evidence of topological flat bands (TFBs) on the surface of bulk RG, which are topologically protected by bulk helical Dirac nodal lines via the bulk-boundary correspondence. Moreover, upon in situ electron doping, the surface TFBs show a splitting with exotic doping evolution, with an order-of-magnitude increase in the bandwidth of the lower split band, and pinning of the upper band near the Fermi level. These experimental observations together with Hartree-Fock calculations suggest that correlation effects are important in this system. Our results demonstrate RG as a platform for investigating the rich interplay between nontrivial band topology, correlation effects, and interaction- driven symmetry-broken states. Significance Searching for materials with both flat bands and nontrivial topology is fundamentally important to realize exotic physical properties. Here, we experimentally report the rhombohedral graphite as an ideal candidate with existence of surface topological flat bands, which are protected by bulk helical Dirac nodal lines. Moreover, the surface topological flat bands show correlation effects, which are evidenced by the splitting and exotic evolution upon in situ electron doping. Our results demonstrate the rhombohedral graphite as a platform for bridging the two interesting fields of nontrivial topological physics and flat-band-induced electronic instabilities.