论文标题
在WSI $ _2 $ n $ _4 $ family中，耦合旋转 - 旋转效果，Rashba效应和隐藏的持续旋转两极分化
Coupled spin-valley, Rashba effect and hidden persistent spin polarization in WSi$_2$N$_4$ family
论文作者
论文摘要
新的二维材料，Mosi $ _2 $ n $ _4 $和WSI $ _2 $ n $ _4 $是成功合成的，并且从理论上预测了各种类似的结构。在这里，我们使用最先进的密度功能理论和多体化功能理论（在G $ _0 $ w $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $ _0 $和BSE），在这里，特别关注wa $ _2 $ z $ _4 $的乐队分裂的电子属性（a = si，ge; z = n，p，as）。由于反转对称性和强旋轨耦合效应破裂，我们在第一个布里鲁因区（BZ）的角落检测到耦合的旋转瓦利效应。此外，我们分别在$γ$和M点上观察到立方体和线性分裂的带。有趣的是，平面镜像对称性（$σ_H$）和降低的任意$ k $ - 点的对称性，强制执行持续的旋转纹理（PST）以完整的BZ发生。我们通过平面外部电场（EEF）打破$σ_H$来诱导RashBA分裂。 W原子的反转不对称位点组群引入了中心对称分层体积的隐藏自旋极化。因此，已经鉴定出了旋转层锁定效应，即能量退化的旋转在顶部和底部W层上的空间隔离。我们的低能$ k.p $模型表明，沿M-K线的PST对EEF和层厚度非常健壮，使其适用于Spintronics和Valleytronics中的应用。
The new two-dimensional materials, MoSi$_2$N$_4$ and WSi$_2$N$_4$ are experimentally synthesized successfully and various similar structures are predicted theoretically. Here, we report the electronic properties with a special focus on the band splitting in WA$_2$Z$_4$ (A=Si, Ge; Z=N, P, As), using state-of-the-art density functional theory and many-body perturbation theory (within the framework of G$_0$W$_0$ and BSE). Due to the broken inversion symmetry and strong spin-orbit coupling effects, we detect coupled spin-valley effects at the corners of the first Brillouin zone (BZ). Additionally, we observe cubically and linearly split bands around the $Γ$ and M points, respectively. Interestingly, the in-plane mirror symmetry ($σ_h$) and the reduced symmetry of arbitrary $k$-point, enforce the persistent spin textures (PST) to occur in full BZ. We induce the Rashba splitting by breaking the $σ_h$ through an out-of-plane external electric field (EEF). The inversion asymmetric site point group of the W atom introduces the hidden spin polarization in centrosymmetric layered bulk counterparts. Therefore, the spin-layer locking effect, namely, energy degenerate opposite spins spatially segregated in the top and bottom W layers, has been identified. Our low energy $k.p$ model demonstrates that the PST along the M-K line is robust to EEF and layer thickness, making them suitable for applications in spintronics and valleytronics.
