AI 中文总结
研究非中心对称系统中磁四极电流，通过构建多极表示建立其产生的对称条件，以从中心对称点群到非中心对称子群转变为例展示电流产生，还揭示边缘积累，为MQ注入及磁化控制提供关键证据。
AI 中文摘要
最近有人提出通过磁八极注入来控制一类新型中心对称反铁磁体（即d波交替磁体）的磁化，其中磁八极是对称性允许的最低阶磁多极子，可作为自旋注入的替代载体。相比之下，在非中心对称反铁磁体中，磁四极（MQ）是对称性允许的最低阶磁多极子，这表明MQ电流可通过MQ注入提供一种控制磁化的有效途径。本文通过构建MQ电导率张量的多极表示，建立了MQ电流产生的对称条件，表明在非中心对称晶体学点群中通常允许MQ电流。作为一个代表性例子，我们展示了在与从中心对称点群（mmm）降低到其非中心对称子群（mm2）相关的线性响应区域中的MQ电流产生。此外，我们揭示了样品边缘附近的MQ积累，类似于自旋霍尔效应引起的自旋积累。这种边缘积累为MQ电流产生提供了直接证据，是在非中心对称反铁磁体中实现MQ注入和基于MQ的磁化控制的关键先决条件。
英文摘要
Magnetization control via magnetic octupole injection has recently been proposed for a new class of centrosymmetric antiferromagnets, namely $d$-wave altermagnets, where the magnetic octupole is the lowest-rank magnetic multipole allowed by symmetry and serves as an alternative carrier to spin injection. In contrast, in noncentrosymmetric antiferromagnets, the magnetic quadrupole (MQ) constitutes the lowest-rank symmetry-allowed magnetic multipole, suggesting that MQ currents can provide an efficient route toward magnetization control through MQ injection. Here, we establish the symmetry conditions for MQ-current generation by constructing the multipole representation of the MQ conductivity tensor and show that MQ currents are generically allowed in noncentrosymmetric crystallographic point groups. As a representative example, we demonstrate MQ-current generation in the linear-response regime associated with symmetry lowering from the centrosymmetric point group ($mmm$) to its noncentrosymmetric subgroup ($mm2$). Furthermore, we reveal MQ accumulation near sample edges, analogous to spin accumulation induced by the spin Hall effect. This edge accumulation provides direct evidence of MQ-current generation and constitutes a key prerequisite for realizing MQ injection and MQ-based magnetization control in noncentrosymmetric antiferromagnets.
Comments29 pages, 6 figures, 6 tables
