论文标题
螺丝对称材料中的立方狄拉克和四倍的Weyl点
Cubic Dirac and quadruple Weyl points in screw-symmetric materials
论文作者
论文摘要
高阶拓扑费在拓扑事项领域具有密集的兴趣。在实际材料中，立方狄拉克点很少见，一个Weyl点（WP）的手性电荷从未被发现超过| c | = 3用于自旋-1/2电子系统。在这项工作中，我们认为，当时间倒流对称性被打破时，一个立方的狄拉克点可以导致一个四倍的WP（| C | = 4带有双带退化），只要这个立方的DIRAC点远离了高对称点，并且涉及八个乐队的耦合，而不是四个乐队，而不是四个乐队，而不是四个乐队来形容一个迪拉克点。八波段可以在带有螺钉对称性的材料中实现。沿着螺钉轴的区域边界附近，折叠带耦合到其“父”带，从而导致希尔伯特空间的两倍。实际上，在“ $ε$ -TAN（带螺钉对称性的太空群体）中，我们在沿螺钉轴上应用Zeeman字段时发现了一个四倍的WP。这个四倍的WP远离高对称点与高度退化的节点不同，在高度对称点上已经报道了高chir量的高度对称性。我们可能会与高chir量相关。拧紧特征值和由此产生的手性电荷。
High-order topological charge is of intensive interest in the field of topological matters. In real materials, cubic Dirac point is rare and the chiral charge of one Weyl point (WP) has never be found to exceed |C| = 3 for spin- 1/2 electronic systems. In this work, we argue that a cubic Dirac point can result in one quadruple WP (|C| = 4 with double band degeneracy) when time-reversal symmetry is broken, provided that this cubic Dirac point is away from the high-symmetry points and involves coupling of eight bands, rather than four bands that were thought to be sufficient to describe a Dirac point. The eight-band manifold can be realized in materials with screw symmetry. Near the zone boundary along the screw axis, the folded bands are coupled to their "parent" bands, resulting in doubling dimension of the Hilbert space. Indeed, in "$ε$-TaN (space group 194 with screw symmetry) we find a quadruple WP when applying a Zeeman field along the screw axis. This quadruple WP away from high symmetry points is distinct from highly degenerate nodes at the high-symmetry points already reported. We further find that such a high chiral charge might be related to the parity mixing of bands with high degeneracy, which in turn alters the screw eigenvalues and the resulted chiral charge.
