AI 中文总结
本文提出自旋空间群（SSGs）框架，可更准确预测磁性材料光学响应，通过模型及第一性原理计算验证其在光吸收、双折射、自旋霍尔响应等方面的有效性。
AI 中文摘要
磁性材料的光学响应通常通过磁空间群（MSGs）进行分类，其中自旋与晶格通过相对论自旋-轨道相互作用锁定。然而，大多数光学可观测量主要由非相对论物理规律支配，因此仅基于MSG的描述可能会忽略重要的物理见解。本文系统表明，在非相对论层面运作的自旋空间群（SSGs）为分析磁性材料的多种光学响应提供了更广泛且更具预测性的框架。聚焦于线性光吸收，本文推导了SSGs施加的变换规则，并表明这些规则会生成有效的实空间点群，可对电荷响应系数施加常规MSG分析无法实现的关联。本文在具有可调自旋-轨道耦合的Lieb晶格交替磁模型中说明了这一基本原理，即使相对论能带分裂变得显著，SSG对线性二色性的预测仍然极为准确。本文进一步通过对两种交替磁候选材料的第一性原理计算确立了该框架的预测能力：锕系化合物UCr₂Si₂C，尽管其自旋-轨道耦合较强且磁对称性呈现明显各向异性，但其光吸收仍几乎各向同性；过渡金属氟化物RbMnF₄，其双折射被仅由SSGs产生的对称性限制在单一平面内。最后，本文将该概念扩展到共面非共线反铁磁体ScMnO₃的自旋霍尔响应，其中SSGs解释了计算得到的自旋霍尔系数的层级关系，证明了其对自旋电子学的直接相关性。
英文摘要
The optical response of magnetic materials is conventionally classified through magnetic space groups (MSGs), where spin and lattice are locked by the relativistic spin-orbit interaction. However, most optical observables are governed primarily by nonrelativistic physics, and thus a purely MSG-based description can overlook important insights. Here we systematically show that spin-space groups (SSGs), which operate at the nonrelativistic level, provide a broader and more predictive framework for analyzing a variety of optical responses of magnets. Focusing on linear optical absorption, we derive the transformation rules imposed by SSGs and show that they generate effective real-space point groups, which can enforce relations among charge response coefficients that are absent from conventional MSG analysis. We illustrate the basic principle in a Lieb-lattice altermagnet model with tunable spin-orbit coupling, where SSG predictions on the linear dichroism remain remarkably accurate even when relativistic band splittings become sizable. We further establish the predictive power of this framework through first-principles calculations on two altermagnetic candidates: the actinide UCr2Si2C, where the optical absorption remains nearly isotropic despite its strong spin-orbit coupling and the pronounced anisotropy apparent from magnetic symmetries, and the transition-metal fluoride RbMnF4, where birefringence is confined to a single plane by symmetries emerging exclusively from SSGs. Finally, we extend the concept to the spin Hall response of the coplanar noncollinear antiferromagnet ScMnO3, where SSGs explain the hierarchy of calculated spin Hall coefficients, demonstrating their direct relevance to spintronics as well.
Comments31 pages, 5 figures
