发表机构
University of Regensburg; École Polytechnique Fédérale de Lausanne (EPFL)（雷根斯堡大学; 洛桑联邦理工学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过第一性原理计算，剖析了FGT与FGaT两种铁磁单层的自旋轨道转矩差异，揭示其电子结构演化对转矩的影响，为层状磁性材料的相关工程提供指导。
AI 中文摘要
我们对铁磁单层Fe₃GeTe₂（FGT）和Fe₃GaTe₂（FGaT）中的自旋轨道转矩开展了系统性第一性原理研究。尽管二者具有相同的晶体结构（点群D₃h）且主要为Fe 3d自旋极化能带，但这两种材料表现出明显不同的电流诱导转矩。我们采用适配对称性的自旋轨道耦合Wannier函数的线性响应理论，计算了转矩率（单位外加电场对应的转矩）的完整角依赖关系，从而揭示了这些差异。FGaT可视为FGT的空穴掺杂类似物，因为Ga比Ge少贡献1个价电子。尽管二者功函数仅相差约28 meV，但K和K'点附近的能带填充发生显著变化：费米能级ε_F处的态密度降低了3倍，且其自旋极化从FGT中的多数自旋逆转为FGaT中的少数自旋。这些电子变化体现在按时间反演奇偶性、子晶格和动量分解的转矩中。特别地，我们在FGaT中识别出显著的隐藏转矩，并将其四次谐波费米海分量的抑制与动量空间 pocket 的演化关联起来。最后，我们在基于对称性的唯象框架内讨论了这类自转矩的出现，而自转矩无法被电流诱导自旋积累的传统图像所捕获。我们的结果为二维铁磁体中的电流诱导转矩提供了微观见解，并为层状磁性材料的缺陷与范德华工程提供了指导。
英文摘要
We present a systematic first-principles study of the spin-orbit torques in the ferromagnetic monolayers Fe$_3$GeTe$_2$ (FGT) and Fe$_3$GaTe$_2$ (FGaT). Despite sharing the same crystal structure (point group $D_{3h}$) and predominantly Fe~$3d$ spin-polarized bands, the two materials exhibit markedly different current-induced torques. We reveal these differences by computing the full angular dependence of the torkance---the torque per unit applied electric field---using linear-response theory with symmetry-adapted spin--orbit-coupled Wannier functions. FGaT may be viewed as a hole-doped analogue of FGT, since Ga contributes one valence electron fewer than Ge. Although the work functions differ by only about $28$~meV, the band filling near $K$ and $K'$ changes substantially: the density of states at $\varepsilon_F$ is reduced by a factor of three and its spin polarization reverses from minority in FGT to majority in FGaT. These electronic changes are reflected in the torques resolved by time-reversal parity, sublattice, and momentum. In particular, we identify pronounced hidden torques in FGaT and relate the suppression of its fourth-harmonic Fermi-sea component to the evolution of momentum-space pockets. Finally, we discuss the emergence of such self-torques, which are not captured by the conventional picture of current-induced spin accumulation, within a symmetry-based phenomenological framework. Our results provide microscopic insight into current-induced torques in two-dimensional ferromagnets and offer guidance for defect and van der Waals engineering of layered magnetic materials.
