Shenzhen Institute for Quantum Science and Engineering and Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China.
Guangdong Provincial Key Laboratory of Computational Science and Material Design, Southern University of Science and Technology, Shenzhen 518055, China.
Phys Rev Lett. 2022 Dec 30;129(27):276601. doi: 10.1103/PhysRevLett.129.276601.
The discovery of hidden spin polarization (HSP) in centrosymmetric nonmagnetic crystals, i.e., spatially distributed spin polarization originated from local symmetry breaking, has promised an expanded material pool for future spintronics. However, the measurements of such exotic effects have been limited to subtle space- and momentum-resolved techniques, unfortunately, hindering their applications. Here, we theoretically predict macroscopic non-reciprocal transports induced by HSP when coupling another spatially distributed quantity, such as staggered local moments in a space-time PT-symmetric antiferromagnet. By using a four-band model Hamiltonian, we demonstrate that HSP plays a crucial role in determining the asymmetric bands with respect to opposite momenta. Such band asymmetry leads to non-reciprocal nonlinear conductivity, exemplified by tetragonal CuMnAs via first-principles calculations. We further provide the material design principles for large nonlinear conductivity, including two-dimensional nature, multiple band crossings near the Fermi level, and symmetry protected HSP. Our Letter not only reveals direct spintronic applications of HSP (such as Néel order detection), but also sheds light on finding observables of other hidden effects, such as hidden optical polarization and hidden Berry curvature.
在中心对称非磁性晶体中发现隐藏的自旋极化（HSP），即源自局部对称破缺的空间分布自旋极化，为未来的自旋电子学提供了扩展的材料库。然而，这些奇异效应的测量一直限于微妙的空间和动量分辨技术，不幸的是，这阻碍了它们的应用。在这里，我们理论预测了 HSP 与另一个空间分布的量（例如时空 PT 对称反铁磁体中的交错局部磁矩）耦合时引起的宏观非互易输运。通过使用四能带模型哈密顿量，我们证明 HSP 在确定相对于相反动量的不对称能带方面起着关键作用。这种带不对称性导致非互易非线性电导率，通过第一性原理计算以四方 CuMnAs 为例进行了说明。我们进一步提供了实现大非线性电导率的材料设计原则，包括二维性质、费米能级附近的多个能带交叉和受对称性保护的 HSP。我们的信件不仅揭示了 HSP 的直接自旋电子学应用（例如奈耳有序检测），而且还揭示了其他隐藏效应的可观察性，例如隐藏的光学极化和隐藏的 Berry 曲率。
