Zhang Ke, Zhao Shixuan, Hao Zhanyang, Kumar Shiv, Schwier Eike F, Zhang Yingjie, Sun Hongyi, Wang Yuan, Hao Yujie, Ma Xiaoming, Liu Cai, Wang Le, Wang Xiaoxiao, Miyamoto Koji, Okuda Taichi, Liu Chang, Mei Jiawei, Shimada Kenya, Chen Chaoyu, Liu Qihang
Department of Physical Science, Graduate School of Science, Hiroshima University, Hiroshima 739-0046, Japan.
Shenzhen Institute for Quantum Science and Technology and Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China.
Phys Rev Lett. 2021 Sep 17;127(12):126402. doi: 10.1103/PhysRevLett.127.126402.
The spin polarization in nonmagnetic materials is conventionally attributed to the outcome of spin-orbit coupling when the global inversion symmetry is broken. The recently discovered hidden spin polarization indicates that a specific atomic site asymmetry could also induce measurable spin polarization, leading to a paradigm shift in research on centrosymmetric crystals for potential spintronic applications. Here, combining spin- and angle-resolved photoemission spectroscopy and theoretical calculations, we report distinct spin-momentum-layer locking phenomena in a centrosymmetric, layered material, BiOI. The measured spin is highly polarized along the Brillouin zone boundary, while the same effect almost vanishes around the zone center due to its nonsymmorphic crystal structure. Our work demonstrates the existence of momentum-dependent hidden spin polarization and uncovers the microscopic mechanism of spin, momentum, and layer locking to each other, thus shedding light on the design metrics for future spintronic materials.
在非磁性材料中，自旋极化通常被认为是在全局反演对称性被打破时自旋 - 轨道耦合的结果。最近发现的隐藏自旋极化表明，特定的原子位不对称性也可以诱导可测量的自旋极化，这导致了在用于潜在自旋电子应用的中心对称晶体研究中出现了范式转变。在这里，结合自旋和角分辨光电子能谱以及理论计算，我们报道了在一种中心对称的层状材料BiOI中存在独特的自旋 - 动量 - 层锁定现象。测量到的自旋沿着布里渊区边界高度极化，而由于其非对称晶体结构，在区中心附近相同的效应几乎消失。我们的工作证明了动量相关的隐藏自旋极化的存在，并揭示了自旋、动量和层相互锁定的微观机制，从而为未来自旋电子材料的设计指标提供了启示。
