Hirayama Motoaki, Okugawa Ryo, Ishibashi Shoji, Murakami Shuichi, Miyake Takashi
Nanosystem Research Institute, AIST, Tsukuba 305-8568, Japan.
Department of Physics, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8551, Japan.
Phys Rev Lett. 2015 May 22;114(20):206401. doi: 10.1103/PhysRevLett.114.206401.
We study Weyl nodes in materials with broken inversion symmetry. We find based on first-principles calculations that trigonal Te and Se have multiple Weyl nodes near the Fermi level. The conduction bands have a spin splitting similar to the Rashba splitting around the H points, but unlike the Rashba splitting the spin directions are radial, forming a hedgehog spin texture around the H points, with a nonzero Pontryagin index for each spin-split conduction band. The Weyl semimetal phase, which has never been observed in real materials without inversion symmetry, is realized under pressure. The evolution of the spin texture by varying the pressure can be explained by the evolution of the Weyl nodes in k space.
我们研究了具有反演对称性破缺的材料中的外尔点。基于第一性原理计算，我们发现三角相的碲（Te）和硒（Se）在费米能级附近有多个外尔点。导带在H点附近具有类似于Rashba分裂的自旋分裂，但与Rashba分裂不同的是，自旋方向是径向的，在H点周围形成刺猬状自旋纹理，每个自旋分裂的导带都有一个非零的庞特里亚金指标。在压力下实现了外尔半金属相，这种相在没有反演对称性的真实材料中从未被观测到。通过改变压力引起的自旋纹理的演变可以用k空间中外尔点的演变来解释。
