Multipole classification in 122 magnetic point groups for unified understanding of multiferroic responses and transport phenomena
Multipole classification in 122 magnetic point groups for unified understanding of multiferroic responses and transport phenomena
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DOI：
10.1103/physrevb.104.054412
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发表时间：
2021-05
影响因子：
3.7
通讯作者：
Megumi Yatsushiro;H. Kusunose;S. Hayami
中科院分区：
文献类型：
--
作者：
Megumi Yatsushiro;H. Kusunose;S. Hayami
固体中的电子自由度（例如电荷、自旋、轨道、亚晶格和键自由度）之间的相互作用是与非常规电子有序态交叉关联现象的来源。这样的自由度可以用四种类型的多极（电的，磁的，磁环的，和电环的）以统一的方式来描述，这使得我们能够以透明的方式将微观自由度与宏观物理响应紧密联系起来。本文利用群论的方法对122个磁点群中的多极子进行了分类。分类是有用的，以确定潜在的积极多极不仅在普通的铁磁和反铁磁排序，但也在奇异的排序打破时间反演对称性，例如，回路电流状态。此外，分类提供了一个洞察的微观起源的交叉相关的响应和量子输运。通过对二阶响应函数的分析，总结了线性磁电、压电和弹性响应以及非线性电导率和能斯特系数等响应函数中不可缺少的多极矩。我们的研究结果极大地促进了功能性多铁性材料的进一步发现，指导下自底向上的材料设计的基础上的自适应多极。
Mutual interplay between the electronic degrees of freedom in solids, such as charge, spin, orbital, sublattice, and bond degrees of freedom, is a source of cross-correlated phenomena with unconventional electronic ordered states. Such degrees of freedom can be described by four types of multipoles (electric, magnetic, magnetic toroidal, and electric toroidal) in a unified way, which enable us to tightly connect the microscopic degrees of freedom with macroscopic physical responses in a transparent manner. We complete a classification of the multipoles in all 122 magnetic point groups based on the group theory. The classification is useful to identify potentially active multipoles not only in ordinary ferromagnetic and antiferromagnetic orderings but also in exotic orderings breaking time-reversal symmetry, e.g., a loop-current state. Moreover, the classification gives an insight into the microscopic origin of the cross-correlated responses and quantum transports. By analyzing response functions up to the second order, we summarize the indispensable multipole moments for various responses, such as the linear magnetoelectric, piezoelectric, and elastic responses, and the nonlinear conductivity and Nernst coefficient. Our results highly promote a further discovery of functional multiferroic materials, guided by the bottom-up material design based on the symmetry-adapted multipoles.