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
State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China.
Department of Physics, Princeton University, Princeton, NJ 08544.
Proc Natl Acad Sci U S A. 2024 Oct 22;121(43):e2410714121. doi: 10.1073/pnas.2410714121. Epub 2024 Oct 16.
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.
平带和非平凡拓扑物理是凝聚态物理的两个重要主题。菱方石墨（RG）具有类似于Su-Schrieffer-Heeger模型的独特堆叠结构，是实现平带和非平凡拓扑物理的潜在候选材料。在此，我们报告了体相RG表面拓扑平带（TFB）的实验证据，这些平带通过体-边界对应关系由体相螺旋狄拉克节线进行拓扑保护。此外，原位电子掺杂后，表面TFB表现出具有奇异掺杂演化的分裂，下分裂带的带宽增加了一个数量级，而上带在费米能级附近钉扎。这些实验观测结果与哈特里-福克计算表明，关联效应在该系统中很重要。我们的结果证明RG是一个用于研究非平凡能带拓扑、关联效应和相互作用驱动的对称破缺态之间丰富相互作用的平台。
