用光拖拽读取交替磁畴

中文摘要 AI 辅助

有限的光子动量允许在中心对称空间群中产生二阶光电流，而常规的体光伏效应在此类空间群中是被禁止的。本文研究交替磁体的光拖拽响应，表明其角依赖关系可同时揭示磁有序的对称性和样品的奈尔磁畴。例如，当晶体旋转交换两个磁畴时，电流的畴偶部分和畴奇部分会出现在不同的角谐波中，对于四方d波交替磁体，分别对应4n和4n+2，因此在单个磁畴上旋转90度进行两次测量即可分离出畴奇电流。我们还发现，这些微观贡献的畴奇偶性取决于光的偏振：线偏振光下，仅位移项为畴奇；圆偏振光下，畴奇通道切换为注入项、费米面项和接触主值项。镜像对称确定各谐波的角相位，并区分d_{x²-y²}、d_{xy}和g波有序。相比之下，常规共线反铁磁体无畴奇光拖拽电流，四方铁磁体中两部分共享相同谐波。尽管交替磁体的自旋劈裂不需要自旋轨道耦合（SOC），但SOC对观测畴奇电荷电流至关重要。本研究揭示了光拖拽中交替磁性的独特特征，为全光读取交替磁体提供了途径。

英文摘要

Finite photon momentum allows second-order photocurrents in centrosymmetric space groups, where the conventional bulk photovoltaic effect is forbidden. Here we study the photon-drag response of altermagnets and show that its angular dependence reveals both the symmetry of the magnetic order and the Néel domain of the sample. For example, when a crystal rotation exchanges the two domains, the domain-even and domain-odd parts of the current appear in different angular harmonics, $4n$ and $4n+2$ for tetragonal $d$-wave altermagnets, so that two measurements rotated by $90^\circ$ on a single domain isolate the domain-odd current. We also find that these microscopic contributions exhibit opposite domain parities depending on light polarization. Under linear light, only the shift term is domain odd, while under circular light, the domain-odd channel switches to the injection, Fermi-surface, and contact principal-value terms. Mirror symmetries fix the angular phase of each harmonic and distinguish $d_{x^2-y^2}$, $d_{xy}$, and $g$-wave order. In contrast, conventional collinear antiferromagnets show no domain-odd photon-drag current, and in tetragonal ferromagnets the two parts share the same harmonics. Although the altermagnetic spin splitting does not require spin-orbit coupling (SOC), SOC is essential to observe the domain-odd charge current. Our work uncovers distinct signatures of altermagnetism in photon drag and provides a route to all optical magnetic readouts of altermagnets.

发表机构

• University of Pennsylvania（宾夕法尼亚大学）

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Submitted, 2 Figures