Node line (NL) band-touchings protected by mirror symmetry (named as m-NL), the product of inversion and time reversal symmetry S=PT (s-NL), or nonsymmorphic symmetry are nontrivial topological objects of topological semimetals (SMs) in the Brillouin Zone (BZ). In this work, we screened the family of MgSrSi-type crystals using first principles calculations, and discovered that more than 70 members are NLSMs. A new type of multi-loop structure was found in AsRhTi that a s-NL touches robustly with a m-NL at some "nexus point", and in the meanwhile a second m-NL crosses with the s-NL to form a Hopf-link. Unlike the previously proposed Hopf-link formed by two s-NLs or two m-NLs, a Hopf-link formed by a s-NL and a m-NL requires a minimal three-band model to characterize its essential electronic structure. The associated topological surface states on different surfaces of AsRhTi crystal were also obtained. Even more complicated and exotic multi-loop structure of NLs were predicted in AsFeNa and PNiNb. Our work may shed light on search for exotic multi-loop NLSMs in real materials.
Cite
@article{arxiv.1807.06247,
title = {Exotic Node Line in ternary MgSrSi-type crystals},
author = {Jinling Lian and Lixian Yu and Qi-Feng Liang and Jian Zhou and Rui Yu and Hongming Weng},
journal= {arXiv preprint arXiv:1807.06247},
year = {2018}
}