Novel electronic states of topological nodal semimetals studied by ARPES

Search for new types of nodal fermions, such as Dirac and Weyl fermions, associated with the crystal symmetry is currently a hot topic in topological materials science. ARPES is an excellent experimental technique to verify new topological materials owing to its unique capability to directly visualize the Dirac-cone energy bands. In this talk, we will present novel electronic states of topological semimetals associated with the mirror and nonsymmorphic symmetry of crystal, such as trigonal tellurium with Weyl nodes protected by screw symmetry [1], CaAgAs with a line node associated with mirror symmetry [2], and line-node semimetal HfSiS showing unexpected Dirac-node arc [3]. We will also discuss interplay between nodal fermions and crystal symmetry in comparison with other topological materials [4,5].

[1] K. Nakayama et al., Phys. Rev. B 95 (2017) 125204.
[2] D. Takane et al., arXiv:1708.06874.
[3] D. Takane et al., Phys. Rev. B 94 (2016) 121108(R).
[4] Y. Tanaka et al., Nature Phys. 8 (2012) 800.
[5] T. Shoman et al., Nature Commun. 6 (2015) 6547.

*This work has been performed in collaboration with D. Takane, K. Nakayama, S. Souma, T. Takahashi (Tohoku Univ.), K. Yamauchi, T. Oguchi (Osaka Univ.), K. Segawa (Kyoto Sangyo Univ.), Z. Wang, and Yoichi Ando (Univ. of Cologne).