The coexistence of ferroelectricity and spin-orbit coupling in noncentrosymmetric systems may allow for a nonvolatile control of spin textures in the momentum space by tuning the ferroelectric polarization. Based on first-principles calculations, supplemented with $\vec{k}·\vec{p}$ analysis, we report the emergence of the reversible spin textures in the two-dimensional (2D) $\mathrm{Ga}XY$ ($X=\mathrm{Se}$, Te; $Y=\mathrm{Cl}$, Br, I) monolayer compounds, a new class of 2D materials exhibiting in-plane ferroelectricity. We find that due to the large in-plane ferroelectric polarization, unidirectional out-of-plane spin textures are induced in the topmost valence band having giant spin splitting. Importantly, such out-of-plane spin textures, which can host a long-lived helical spin mode known as a persistent spin helix, can be fully reversed by switching the direction of the in-plane ferroelectric polarization. We show that the application of an external in-plane electric field oriented oppositely to the in-plane ferroelectric polarization direction is an effective method to flip the orientation of the out-of-plane spin textures. Thus, our findings can open avenues for interplay between the unidirectional out-of-plane spin textures and the in-plane ferroelectricity in 2D materials, which is useful for efficient and nonvolatile spintronic devices.

中文翻译：

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在二维 GaXY(X=Se, Te;Y=Cl, Br, I) 化合物中具有巨大自旋分裂的可逆自旋结构，用于持久自旋螺旋

非中心对称系统中铁电性和自旋轨道耦合的共存可以通过调整铁电极化来对动量空间中的自旋纹理进行非易失性控制。基于第一性原理计算，辅以$\overrightarrow{克}·\overrightarrow{磷}$ 分析，我们报告了二维（2D）中可逆自旋纹理的出现 $嘎X是$ ($X=硒$, 特; $是=氯$, Br, I) 单层化合物，一类具有面内铁电性的新型二维材料。我们发现由于大的面内铁电极化，在具有巨大自旋分裂的最顶层价带中诱导了单向面外自旋纹理。重要的是，这种面外自旋纹理可以通过改变面内铁电极化的方向来完全逆转，它可以承载被称为持久自旋螺旋的长寿命螺旋自旋模式。我们表明，应用与面内铁电极极化方向相反的外部面内电场是翻转面外自旋纹理方向的有效方法。因此，