The presence of a Dirac nodal line in a time-reversal and inversion symmetric system is dictated by the Z2 index when spin-orbit interaction is absent. In a first principles calculation, we show that a Dirac nodal line can emerge in Z2 trivial material by calculating the band structure of SnSe in a face centered cubic lattice as an example. We qualitatively show that it becomes a topological crystalline insulator when spin-orbit interaction is taken into account. We clarify the origin of the Dirac nodal line by obtaining irreducible representations corresponding to bands and explain the triviality of the Z2 index. We construct an effective model representing the Dirac nodal line using the {\bf k}⋅{\bf p} method, and discuss the Berry phase and a surface state expected from the Dirac nodal line.
@article{arxiv.1804.01240,
title = {Face centered cubic SnSe as a $\mathbb{Z}_2$ trivial Dirac nodal line material},
author = {Ikuma Tateishi and Hiroyasu Matsuura},
journal= {arXiv preprint arXiv:1804.01240},
year = {2018}
}