标题： 共线反铁磁体及其朗道理论 显示英文标题

标题： Collinear Altermagnets and their Landau Theories

摘要： 反铁磁体在零自旋轨道耦合（SOC）极限下表现出自发的自旋分裂电子能带，这是由于存在共线补偿磁序所致。 反铁磁体独特的磁晶对称性确保了这些自旋分裂在晶体动量空间中具有特征各向异性。 由于它们在自旋电子学中的应用潜力，这些系统引起了广泛关注。 在本文中，我们提供了一个通用的朗道理论，涵盖了所有三维反铁磁体，其中磁序不会扩大晶胞。 我们确定了所有允许反铁磁性的晶体结构，然后将其简化为相对较少的一组不同的朗道理论，用于描述此类系统。 在零SOC极限下，我们确定了与能带结构自旋分裂相关的可能局部多极序。 我们明确地阐明了在零SOC下定义的反铁磁性（“理想”反铁磁体）与弱SOC效应之间的联系。 特别是，我们研究了当SOC存在时由对称性允许的哪些响应函数是由无自旋轨道耦合理论保证的，并阐述了反铁磁体与传统共线反铁磁体相比的独特性质。 最后，我们通过考虑一些反铁磁候选材料来说明这些概念的应用。 显示英文摘要

摘要： Altermagnets exhibit spontaneously spin-split electronic bands in the zero spin-orbit coupling (SOC) limit arising from the presence of collinear compensated magnetic order. The distinctive magneto-crystalline symmetries of altermagnets ensure that these spin splittings have a characteristic anisotropy in crystal momentum space. These systems have attracted a great deal of interest due to their potential for applications in spintronics. In this paper, we provide a general Landau theory that encompasses all three-dimensional altermagnets where the magnetic order does not enlarge the unit cell. We identify all crystal structures that admit altermagnetism and then reduce these to a relatively small set of distinct possible Landau theories governing such systems. In the zero SOC limit, we determine the possible local multipolar orders that are tied to the spin splitting of the band structure. We make precise the connection between altermagnetism as defined at zero SOC ("ideal" altermagnets) and the effects of weak SOC. In particular, we examine which response functions allowed by symmetry when SOC is present are guaranteed by the spin-orbit free theory, and spell out the distinctive properties of altermagnets in comparison with conventional collinear antiferromagnets. Finally, we show how these ideas can be applied by considering a number of altermagnetic candidate materials.