Flat Band and ℤ<sub>2</sub> Topology of Kagome Metal CsTi<sub>3</sub>Bi<sub>5</sub>
Yuan Wang, Yixuan Liu, Zhanyang Hao, Wenjing Cheng, Junze Deng, Yuxin Wang, Yuhao Gu, Xiao‐Ming Ma, Hongtao Rong, Fayuan Zhang, Shu Guo, Chengcheng Zhang, Zhicheng Jiang, Yichen Yang, Wan‐Ling Liu, Qi Jiang, Zhengtai Liu, Mao Ye, Dawei Shen, Yi Liu, Shengtao Cui, Le Wang, Cai Liu, Junhao Lin, Ying Liu, Yongqing Cai, Jinlong Zhu, Kai Chen, Jia‐Wei Mei
Abstract
The simple kagome-lattice band structure possesses Dirac cones, flat band, and saddle point with van Hove singularities in the electronic density of states, facilitating the emergence of various electronic orders. Here we report a titanium-based kagome metal CsTi 3 Bi 5 where titanium atoms form a kagome network, resembling its isostructural compound CsV 3 Sb 5 . Thermodynamic properties including the magnetization, resistance, and heat capacity reveal the conventional Fermi liquid behavior in the kagome metal CsTi 3 Bi 5 and no signature of superconducting or charge density wave (CDW) transition anomaly down to 85 mK. Systematic angle-resolved photoemission spectroscopy measurements reveal multiple bands crossing the Fermi level, consistent with the first-principles calculations. The flat band formed by the destructive interference of hopping in the kagome lattice is observed directly. Compared to CsV 3 Sb 5 , the van Hove singularities are pushed far away above the Fermi level in CsTi 3 Bi 5 , in line with the absence of CDW. Furthermore, the first-principles calculations identify the nontrivial ℤ 2 topological properties for those bands crossing the Fermi level, accompanied by several local band inversions. Our results suppose CsTi 3 Bi 5 as a complementary platform to explore the superconductivity and nontrivial band topology.