发表机构
University of Florida（佛罗里达大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过计算双磁振子光散射强度，发现交替磁体的磁振子劈裂使高能谱特征移动并与交换各向异性线性相关，为识别交替磁有序提供了光谱学方法。
AI 中文摘要
交替磁性是最近确立的一类磁性有序，它结合了完全补偿的磁矩与动量依赖的自旋劈裂，然而识别其光谱指纹仍是一个开放的挑战。在本工作中，我们通过计算不同偏振通道中的双磁振子光散射强度，研究了二维$d$波交替磁体中的有限动量双磁振子激发。利用线性自旋波理论并进一步纳入领先的$1/S$量子修正，我们证明交替磁体的特征磁振子劈裂将双磁振子连续谱的上边缘及相应光谱特征在$\boldsymbol{X}=(\pi,0)$处相对于常规反铁磁体移向更高能量，其位移量与交换各向异性$|\delta J_2|$成线性关系，而布里渊区中心处的响应保持不变。尽管磁振子-磁振子相互作用强烈地将谱权重重新分布到较低能量，与高能动量选择性重构相关的能量尺度仍然稳健。相互作用还产生了一个在低能下显著的双峰结构，该结构在线性自旋波理论中没有对应物。在$\boldsymbol{K}=(\pi/2,\pi/2)$处，我们展示了在常规反铁磁相中相互作用的双磁振子共振是双重简并的，而有限的交替磁交换各向异性解除了这一简并，产生两个峰，其间距与$|\delta J_2|$成线性关系。这两个特征背后的特征能量尺度是双磁振子扇区固有的，而非特定散射算符所特有。这些发现凸显了有限动量双磁振子光谱学在识别绝缘磁体中的交替磁有序方面的潜力，并推动了针对候选交替磁体材料的动量分辨共振非弹性X射线散射研究。
英文摘要
Altermagnetism is a recently established class of magnetic order that combines fully compensated moments with momentum-dependent spin splitting, yet identifying its spectroscopic fingerprints remains an open challenge. In this work, we investigate finite-momentum two-magnon excitations in a two-dimensional $d$-wave altermagnet by calculating the two-magnon light scattering intensity in different polarization channels. Using linear spin-wave theory and further incorporating the leading $1/S$ quantum corrections, we demonstrate that the characteristic magnon splitting of altermagnets shifts the upper edge of the two-magnon continuum and the corresponding spectral features to higher energy at $\boldsymbol{X}=(π,0)$ relative to the conventional antiferromagnet, by an amount linear in the exchange anisotropy $|δJ_2|$, while leaving the response at the Brillouin-zone center unchanged. Although magnon-magnon interactions strongly redistribute spectral weight toward lower energies, the energy scale associated with the high-energy momentum-selective reconstruction remains robust. The interactions additionally generate a pronounced low-energy two-peak structure that has no counterpart within linear spin-wave theory. At $\boldsymbol{K}=(π/2,π/2)$, we show that the interacting two-magnon resonance is twofold degenerate in the conventional antiferromagnetic phase, while a finite altermagnetic exchange anisotropy lifts this degeneracy, producing two peaks whose separation is linear in $|δJ_2|$. The characteristic energy scales underlying both features are intrinsic to the two-magnon sector rather than to a specific scattering operator. These findings highlight the potential of finite-momentum two-magnon spectroscopy for identifying altermagnetic order in insulating magnets and motivate momentum-resolved resonant inelastic x-ray scattering studies of candidate altermagnetic materials.
