Science Bulletin 67, 1954-1957 (2022)
Deping Guo#, Pengjie Guo#, Shijing Tan, Min Feng, Limin Cao, Zheng-Xin Liu*, Kai Liu*, Zhong-Yi Lu, Wei Ji*
Abstract
Dirac nodal-line semimetals (DNLSMs) host novel quasiparticle excitations and intriguing transport properties, which are, however, easily perturbed under strong spin-orbit coupling (SOC), especially in low-dimensions. Two-dimensional (2D) layers have numerous advantages and are under continuous development; however, 2D-DNLSMs resistant to SOC are yet to be discovered. Here, we report the C_2v×Z_2^T little co-group, a non-symmorphic symmetry we found in 2D, guarantees a robust 2D-DNLSM against SOC, which could be imposed in three-atomic-layer (3-AL) Bismuth (the brick phase, a novel Bi allotrope) and other layered materials. Intriguingly, (4n+2) valence electrons fill the electronic bands in 3-AL Bi, such that the nodal line passes the Fermi level where other low-energy states are gapped, allowing feasible observation of DNLSM-induced phenomena without interference from other bands in future transport measurements. Thus, our study demonstrates an unprecedented category of layered materials, allowing for the exploration of nearly isolated DNL states in 2D.
