近日，清华大学物理系的周树云及其研究团队取得一项新进展。经过不懈努力，他们对菱形石墨中的关联拓扑平带进行研究。相关研究成果已于2024年10月16日在国际知名学术期刊《美国科学院院刊》上发表。
该研究团队报道了在体相菱形石墨（RG）表面观测到拓扑平带（TFBs）的实验证据，这些能带通过体-边对应关系受到体相螺旋狄拉克节点线的拓扑保护。此外，通过原位电子掺杂，表面TFBs展现出奇特的掺杂演化分裂现象，其中较低分裂能带的带宽增加一个数量级，而较高能带则锚定在费米能级附近。
这些实验观测结果与Hartree-Fock计算共同表明，在该系统中关联效应起着重要作用。这项研究结果展示了RG作为研究非平凡能带拓扑、关联效应以及相互作用驱动的对称性破缺态之间丰富相互作用的平台价值。
据悉，平带与非平凡拓扑物理是凝聚态物理中的两个重要课题。菱形石墨（RG）凭借其类似于Su-Schrieffer-Heeger模型的独特堆叠构型，成为同时实现平带与非平凡拓扑物理的潜在候选材料。
附：英文原文
Title: Correlated topological flat bands in rhombohedral graphite
Author: 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
Issue&Volume: 2024-10-16
Abstract: 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.
DOI: 10.1073/pnas.2410714121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2410714121
来源：科学网 小柯机器人