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arXiv · 2201.12851

Type-II Dirac Nodal Lines in double-kagome-layered CsV$_8$Sb$_{12}$

Yongqing Cai·Jianfeng Wang·Yuan Wang·Zhanyang Hao·Yixuan Liu·Zhicheng Jiang·Xuelei Sui·Xiaoming Ma·Chengcheng Zhang·Zecheng Shen·Yichen Yang·Wanling Liu·Qi Jiang·Zhengtai Liu·Mao Ye·Dawei Shen·Yi Liu·Shengtao Cui·Le Wang·Cai Liu·Junhao Lin·Bing Huang·Jia-Wei Mei·Chaoyu Chen
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Abstract

Lorentz-violating type-II Dirac nodal line semimetals (DNLSs), hosting curves of band degeneracy formed by two dispersion branches with the same sign of slope, represent a novel states of matter. While being studied extensively in theory, convincing experimental evidences of type-II DNLSs remain elusive. Recently, Vanadium-based kagome materials have emerged as a fertile ground to study the interplay between lattice symmetry and band topology. In this work, we study the low-energy band structure of double-kagome-layered CsV$_8$Sb$_{12}$ and identify it as a scarce type-II DNLS protected by mirror symmetry. We have observed multiple DNLs consisting of type-II Dirac cones close to or almost at the Fermi level via angle-resolved photoemission spectroscopy (ARPES). First-principle analyses show that spin-orbit coupling only opens a small gap, resulting effectively gapless ARPES spectra, yet generating large spin Berry curvature. These type-II DNLs, together with the interaction between a low-energy van Hove singularity and quasi-1D band as we observed in the same material, suggest CsV$_8$Sb$_{12}$ as an ideal platform for exploring novel transport properties such as chiral anomaly, the Klein tunneling and fractional quantum Hall effect.

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Yongqing Cai, Jianfeng Wang, Yuan Wang, Zhanyang Hao, Yixuan Liu, Zhicheng Jiang, Xuelei Sui, Xiaoming Ma, Chengcheng Zhang, Zecheng Shen, Yichen Yang, Wanling Liu, Qi Jiang, Zhengtai Liu, Mao Ye, Dawei Shen, Yi Liu, Shengtao Cui, Le Wang, Cai Liu, Junhao Lin, Bing Huang, Jia-Wei Mei, Chaoyu Chen. 2022-01-30. Type-II Dirac Nodal Lines in double-kagome-layered CsV$_8$Sb$_{12}$. https://doi.org/10.1002/aelm.202300212

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