反对称动力学自旋关联：自旋空间群约束与频率动量求和规则
Antisymmetric Dynamical Spin Correlations: Spin-Space-Group Constraints and Frequency-Moment Sum Rules
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中文总结 AI 辅助
该研究推导了动力学自旋结构因子反对称部分的对称性约束与频率动量求和规则，通过线性自旋波计算验证了其在交替磁体和螺旋模型中的适用性，为探测磁激发手征性提供了理论依据。
中文摘要 AI 辅助
极化非弹性中子散射通过动力学自旋结构因子张量的自旋分量反对称部分探测磁激发的手征性。我们推导了其在磁空间群与自旋空间群的幺正和反幺正剩余操作下的对称性约束，这些约束确定了允许的张量分量、它们在动量反转下的宇称以及对称性强制节点。随后我们引入了对应的反对易子谱函数，并推导了其频率矩的绝对零度求和规则：第零矩由均匀磁化强度确定；对于海森堡或XXZ交换哈密顿量，xy分量的第一矩由动量加权的静态矢量手征性确定。对于补偿共线反铁磁体，当反演或平移关联相反自旋子晶格时，反对称动力学结构因子被禁止；而在旋转相关的交替磁体中，一般波矢下允许存在动量反转偶宇称的xy分量，因此有限的反对称谱权重可与反对易子谱函数的第零和第一矩消失共存。相比之下，在平面螺旋中，剩余反幺正自旋空间群对称性使允许的xy分量在动量反转下为奇宇称，其第一矩通常非零，且通过第一矩求和规则由动量加权的静态矢量手征性确定。对代表性交替磁体和螺旋模型的线性自旋波计算明确验证了这些对称性与求和规则约束。
英文摘要
Polarized inelastic neutron scattering probes the handedness of magnetic excitations through the spin-component-antisymmetric part of the dynamical spin-structure-factor tensor. We derive its symmetry constraints under unitary and antiunitary residual operations of magnetic space groups and spin-space groups. These constraints determine the allowed tensor components, their parity under momentum reversal, and symmetry-enforced nodes. We then introduce the corresponding antisymmetric commutator spectral function and derive exact zero-temperature sum rules for its frequency moments. The zeroth moment is fixed by the uniform magnetization. For Heisenberg or XXZ exchange Hamiltonians, the first moment of the $xy$ component is fixed by a momentum-weighted static vector chirality. For compensated collinear antiferromagnets, the antisymmetric dynamical structure factor is forbidden when inversion or a translation relates the opposite-spin sublattices. In rotation-related altermagnets, however, an $xy$ component that is even under momentum reversal is allowed at generic wave vectors. Finite antisymmetric spectral weight can therefore coexist with vanishing zeroth and first moments of the commutator spectral function. In a planar helix, by contrast, a residual antiunitary spin-space-group symmetry makes the allowed $xy$ component odd under momentum reversal. Its first moment is generally nonzero and is fixed by a momentum-weighted static vector chirality through the first-moment sum rule. Linear spin-wave calculations for representative altermagnetic and helical models explicitly realize these symmetry and sum-rule constraints.
