XAuBi (X=Eu, Ba)拓扑nodal chain半金属的第一性原理研究

由于在磁性材料体系中缺失时间反演对称性，导致nodal chain被破坏，所以nodal chain通常存在于非磁材料中。但是，磁性材料EuAuBi是与常规磁性材料不同。本工作以第一性原理计算为研究方法，预言了在不考虑自旋轨道相互作用时，磁性材料EuAuBi体系为新型拓扑nodal chain半金属；当考虑自旋轨道耦合时，EuAuBi会退化为外尔半金属。对于非磁材料BaAuBi来说，在不考虑自旋轨道相互作用时，它同样是一种拓扑nodal chain半金属；当考虑自旋轨道相互作用时，由于C3旋转对称性的存在，BaAuBi会退化为狄拉克半金属。在XAuBi (X=Eu, Ba)中发现nodal chain半金属，会促进对六角材料的拓扑性质研究以及开拓其新实际应用领域。

Investigation of Topological Nodal Chain Semimetals in XAuBi (X=Eu, Ba) by the First Principles Calculations

The nodal chain usually exists in the non-magnetic materials, because that the lack of the time reversal symmetry in the magnetic materials tends to kill the nodal chain. However, EuAuBi is an exception, existing nodal chain in the antiferromagnetic state. Based on first-principle calculations, we propose that EuAuBi is a topological nodal chain semimetal (NCSM), in absence of spin orbital coupling (SOC). Whereas, in the presence of SOC, it is a weyl semimetal. For nonmagnetic compound of BaAuBi, it is also a NCSM ignoring SOC. Nonetheless, BaAuBi is a Dirac semimetal due to the crystal symmetry, considering SOC. The discovery of the NCSM phase in XAuBi (X=Eu, Ba) would promote further research on the topological properties of hexagonal materials and develop its new practical applications.