Flat bands, non-trivial band topology and rotation symmetry breaking in layered kagome-lattice RbTi3Bi5
Zhicheng Jiang, Zhengtai Liu, Haiyang Ma, Wei Xia, Zhonghao Liu, Jishan Liu, Soo-hyun Cho, Yichen Yang, Jianyang Ding, Jiayu Liu, Zhe Huang, Yuxi Qiao, Jiajia Shen, Wenchuan Jing, Xiangqi Liu, Jianpeng Liu, Yanfeng Guo, Dawei Shen, Xiangqi Liu, Jianpeng Liu, Jianpeng Liu, Yanfeng Guo, Dawei Shen
Abstract
Abstract A representative class of kagome materials, AV 3 Sb 5 (A = K, Rb, Cs), hosts several unconventional phases such as superconductivity, $${{\mathbb{Z}}}_{2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow> <mml:mi>Z</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:math> non-trivial topological states, and electronic nematic states. These can often coexist with intertwined charge-density wave states. Recently, the discovery of the isostructural titanium-based single-crystals, ATi 3 Bi 5 (A = K, Rb, Cs), which exhibit similar multiple exotic states but without the concomitant charge-density wave, has opened an opportunity to disentangle these complex states in kagome lattices. Here, we combine high-resolution angle-resolved photoemission spectroscopy and first-principles calculations to investigate the low-lying electronic structure of RbTi 3 Bi 5 . We demonstrate the coexistence of flat bands and several non-trivial states, including type-II Dirac nodal lines and $${{\mathbb{Z}}}_{2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow> <mml:mi>Z</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:math> non-trivial topological surface states. Our findings also provide evidence for rotational symmetry breaking in RbTi 3 Bi 5 , suggesting a directionality to the electronic structure and the possible emergence of pure electronic nematicity in this family of kagome compounds.