Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
Phys Rev Lett. 2012 Jun 29;108(26):266802. doi: 10.1103/PhysRevLett.108.266802. Epub 2012 Jun 27.
We perform a complete classification of two-band k·p theories at band crossing points in 3D semimetals with n-fold rotation symmetry and broken time-reversal symmetry. Using this classification, we show the existence of new 3D topological semimetals characterized by C(4,6)-protected double-Weyl nodes with quadratic in-plane (along k(x,y)) dispersion or C(6)-protected triple-Weyl nodes with cubic in-plane dispersion. We apply this theory to the 3D ferromagnet HgCr(2)Se(4) and confirm it is a double-Weyl metal protected by C(4) symmetry. Furthermore, if the direction of the ferromagnetism is shifted away from the [001] axis to the [111] axis, the double-Weyl node splits into four single Weyl nodes, as dictated by the point group S(6) of that phase. Finally, we discuss experimentally relevant effects including the splitting of multi-Weyl nodes by applying a C(n) breaking strain and the surface Fermi arcs in these new semimetals.
我们在具有 n 重旋转对称和时间反演破缺的 3D 半金属中，在能带交叉点处对双带 k·p 理论进行了完整分类。利用这一分类，我们展示了存在新的 3D 拓扑半金属的可能性，其特征是具有二次面内（沿 k(x,y)）色散的 C(4,6)-保护的双 Weyl 节点，或具有立方面内色散的 C(6)-保护的三重 Weyl 节点。我们将这一理论应用于 3D 铁磁体 HgCr(2)Se(4)，并证实其为 C(4)对称性保护的双 Weyl 金属。此外，如果铁磁性的方向偏离[001]轴到[111]轴，双 Weyl 节点将根据该相的点群 S(6)分裂为四个单 Weyl 节点。最后，我们讨论了包括通过施加 C(n)应变来分裂多 Weyl 节点以及在这些新的半金属中存在表面费米弧等与实验相关的效应。
