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中国物理学会期刊

自旋磁化的塞曼量子几何视角

Spin magnetization from the perspective of Zeeman quantum geometry

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  • 自旋磁化是自旋电子学的重要研究方向之一.在中心反演对称性破缺的材料中,外加电场不仅能诱导非平衡自旋极化,即外禀Edelstein效应,还可以通过电子结构重整产生平衡态磁电耦合,即内禀Edelstein磁电效应.在中心对称体系中,近期研究进一步提出了二阶非线性Edelstein效应.通过将自旋自由度引入量子距离并定义新的塞曼量子几何张量,可以建立直流电场驱动下自旋磁化效应的统一理论描述:在线性响应区间,外禀自旋磁化由塞曼贝里曲率主导,而内禀自旋磁化由塞曼量子度规决定;在二阶非线性响应中,非线性Drude项与二阶内禀项与塞曼贝里曲率偶极矩密切相关,而二阶外禀磁化则由塞曼量子度规偶极矩决定.最后,本文展示了各项自旋磁化响应系数的对称性选择定则及候选材料,讨论了交变电场诱导下动力学自旋磁化效应的塞曼量子几何解释,并展望了电场诱导自旋磁化在奈尔力矩产生和磁序电学操控等自旋电子学方面的应用.

     

    Spin magnetization is an important research topic in spintronics. In inversion-symmetry-broken materials, an applied electric field can not only induce a nonequilibrium spin polarization, namely the extrinsic Edelstein effect, but also generate an equilibrium magnetoelectric coupling through the renormalization of the electronic structure, namely the intrinsic Edelstein magnetoelectric effect. In centrosymmetric systems, recent studies have further proposed the emergence of second-order nonlinear Edelstein effects. By incorporating the spin degree of freedom into the quantum distance and introducing a novel Zeeman quantum geometric tensor, a unified theoretical description of spin-magnetization effects driven by dc electric fields is introduced in this perspective. In the linear-response regime, the extrinsic spin magnetization is governed by the Zeeman Berry curvature, whereas the intrinsic spin magnetization is determined by the Zeeman quantum metric. In the second-order nonlinear regime, the nonlinear Drude term and the second-order intrinsic contribution are closely related to Zeeman Berry-curvature dipole, while the second-order extrinsic magnetization is determined by the Zeeman quantum-metric dipole. Finally, we present symmetry-selection rules and candidate materials for various magnetization responses, discuss the Zeeman-quantum-geometric interpretation of dynamical spin magnetization induced by an ac electric field, and highlight the potential applications of electric-field-induced spin magnetization in Néel torque generation and electrical control of magnetic order.

     

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