Composite topological nodal lines penetrating the Brillouin zone in orthorhombic AgF2

• Published in: npj computational materials 2019-04, Vol.5 (1), Article 53
• Main Authors: Shao, Dexi, Wang, Huaiqiang, Chen, Tong, Lu, Pengchao, Gu, Qinyan, Sheng, Li, Xing, Dingyu, Sun, Jian
• Format: Article
• Language: English
• Subjects: 639/766; 639/766/119; 639/766/119/2792; Brillouin zones; Chain scission; Chains; Characterization and Evaluation of Materials; Chemistry and Materials Science; Computational Intelligence; Materials Science; Mathematical analysis; Mathematical and Computational Engineering; Mathematical and Computational Physics; Mathematical Modeling and Industrial Mathematics; Permutations; Spin-orbit interactions; Symmetry; Theoretical
• ISSN: 2057-3960; 2057-3960
• DOI: 10.1038/s41524-019-0190-3

It has recently been found that nonsymmorphic symmetries can bring many exotic band crossings. Here, based on symmetry analysis, we predict that materials with time-reversal symmetry in the space group of Pbca (No. 61) possess rich symmetry-enforced band crossings, including nodal surfaces, fourfold degenerate nodal lines and hourglass Dirac loops, which appear in triplets as ensured by the cyclic permutation symmetry. We take Pbca AgF 2 as an example in real systems and studied its band structures with ab initio calculations. Specifically, in the absence of spin-orbit coupling (SOC), besides the above-mentioned band degeneracies, this system features a nodal chain and a nodal armillary sphere penetrating the Brillouin zone (BZ). While with SOC, we find a new configuration of the hourglass Dirac loop/chain with the feature traversing the BZ, which originates from the splitting of a Dirac loop confined in the BZ. Furthermore, guided by the bulk-surface correspondence, we calculated the surface states to explore these bulk nodal phenomena. The evolution of these interesting nodal phenomena traversing the BZ under two specific uniaxial strains is also discussed.