近日，上海科技大学的刘建鹏及其研究小组与美国普林斯顿大学的M. Zahid Hasan等人合作并取得一项新进展。经过不懈努力，他们提出反铁磁笼目金属FeGe中用于描述电荷密度波和轨道通量态的理论。相关研究成果已于2024年4月1日在国际知名学术期刊《中国物理快报》上发表。

该研究团队从理论上研究了一种新型反铁磁性金属铁锗的电荷序和轨道磁性。基于第一性原理密度泛函理论计算，研究人员研究了反铁磁笼目金属FeGe的电子结构、费米表面量子涨落和声子性质。研究发现，电子-电子相互作用与电子-声子耦合之间微妙的协同作用，在这种系统中催生了电荷密度波。这种相互作用导致了声子不稳定的非寻常现象，最终形成了电荷密度波（CDW）状态。

研究人员进一步表明，在CDW阶段，基态电流密度分布呈现出一个有趣的六芒星模式，导致磁通密度调制。该系统中的轨道通量(或电流环)是磁性、晶格几何形状、电荷序和自旋轨道耦合(SOC)之间微妙相互作用的结果，可以用一个简单而通用的紧束缚理论来描述，其中包括Kane–Mele型SOC项和磁交换相互作用。研究人员进一步研究了FeGe中特殊阶跃边缘态的起源，揭示了这种新型笼目反铁磁材料的拓扑性质和关联效应。

附：英文原文

Title: Theory for Charge Density Wave and Orbital-Flux State in Antiferromagnetic Kagome Metal FeGe

Author:Hai-Yang Ma^1,2,3, Jia-Xin Yin⁴, M. Zahid Hasan^4,5,6, and Jianpeng Liu^1,2,7*

Issue&Volume: 2024-04-01

Abstract: We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe. Based on first-principles density functional theory calculations, we study the electronic structures, Fermi-surface quantum fluctuations, as well as phonon properties of the antiferromagnetic kagome metal FeGe. It is found that charge density wave emerges in such a system due to a subtle cooperation between electron–electron interactions and electron–phonon couplings, which gives rise to an unusual scenario of interaction-triggered phonon instabilities, and eventually yields a charge density wave (CDW) state. We further show that, in the CDW phase, the ground-state current density distribution exhibits an intriguing star-of-David pattern, leading to flux density modulation. The orbital fluxes (or current loops) in this system emerge as a result of the subtle interplay between magnetism, lattice geometries, charge order, and spin-orbit coupling (SOC), which can be described by a simple, yet universal, tight-binding theory including a Kane–Mele-type SOC term and a magnetic exchange interaction. We further study the origin of the peculiar step-edge states in FeGe, which sheds light on the topological properties and correlation effects in this new type of kagome antiferromagnetic material.

DOI: 10.1088/0256-307X/41/4/047103

Source: https://cpl.iphy.ac.cn/10.1088/0256-307X/41/4/047103