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arXiv 2402.10201cond-mat.mes-hallcond-mat.mtrl-scicond-mat.str-el
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交变磁体中的镜面陈能带与外尔节线环

Mirror Chern Bands and Weyl Nodal Loops in Altermagnets

Daniil S. Antonenko, Rafael M. Fernandes, Jorn W. F. Venderbos

AI总结:

本文研究交变磁体中磁矩方向对拓扑电子能谱的影响,发现面外磁矩下二维体系经SOC打开狄拉克交叉能隙形成镜面陈能带并实现量子自旋霍尔效应,三维体系则形成受镜面对称保护的外尔节线环。

摘要:

由于时间反演对称性与晶体对称性之间独特的相互作用,交变磁体的电子能谱是产生非平凡拓扑的沃土。这体现在相反自旋能带之间非常规的塞曼劈裂上,该劈裂在无自旋轨道耦合(SOC)的情况下出现,并沿高对称方向呈现节点。在此,我们论证即使对于较小的SOC,交变磁态中磁矩的方向也会对电子能谱产生深远影响,从而使新颖的拓扑现象得以出现。通过研究二维(2D)和三维(3D)交变磁体的微观模型(部分动机来自金红石材料),我们展示了迄今未被探索的、相同自旋但相反子格能带之间的狄拉克交叉的出现。磁矩的方向决定了当SOC开启时这些交叉的命运。我们重点关注面外磁矩的情形,该情形禁止反常霍尔效应,从而确保在交变磁态中不会触发弱磁化。在二维模型中,SOC使狄拉克交叉打开能隙,产生能够实现量子自旋霍尔效应的镜面陈能带,并且随着磁矩幅值的增大,这些能带经历向平庸能带的拓扑转变。另一方面,在三维模型中,即使存在SOC,交叉仍然持续存在,形成受镜面对称性保护的外尔节线环。最后,我们讨论了在候选交变磁体材料中调控这些效应的可能途径。

英文摘要:

The electronic spectra of altermagnets are a fertile ground for nontrivial topology due to the unique interplay between time-reversal and crystalline symmetries. This is reflected in the unconventional Zeeman splitting between bands of opposite spins, which emerges in the absence of spin-orbit coupling (SOC) and displays nodes along high-symmetry directions. Here, we argue that even for a small SOC, the direction of the magnetic moments in the altermagnetic state has a profound impact on the electronic spectrum, enabling novel topological phenomena to appear. By investigating microscopic models for two-dimensional (2D) and three-dimensional (3D) altermagnets, motivated in part by rutile materials, we demonstrate the emergence of hitherto unexplored Dirac crossings between bands of the same spin but opposite sublattices. The direction of the moments determines the fate of these crossings when the SOC is turned on. We focus on the case of out-of-plane moments, which forbid an anomalous Hall effect and thus ensure that no weak magnetization is triggered in the altermagnetic state. In the 2D model, the SOC gaps out the Dirac crossings, resulting in mirror Chern bands that enable the Quantum Spin Hall Effect and undergo a topological transition to trivial bands upon increasing the magnitude of the magnetic moment. On the other hand, in the 3D model the crossings persist even in the presence of SOC, forming Weyl nodal loops protected by mirror symmetry. Finally, we discuss possible ways to control these effects in altermagnetic material candidates.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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