论文标题
局部杂质状态对磁性拓扑绝缘子中交换耦合机制的无处不在的影响
Ubiquitous impact of localised impurity states on the exchange coupling mechanism in magnetic topological insulators
论文作者
论文摘要
Since the discovery of the quantum anomalous Hall effect in the magnetically doped topological insulators (MTI) Cr:(Bi,Sb)$_2$Te$_3$ and V:(Bi,Sb)$_2$Te$_3$, the search for the exchange coupling mechanisms underlying the onset of ferromagnetism has been a central issue, and a variety of different scenarios have been put forward.通过结合谐振光发射，X射线磁性二色性和多重配体场理论，我们确定了（BI，SB）$ _ 2 $ TE $ _3 $中V和CR杂质的局部电子和磁性构型。尽管发现两种掺杂剂类型的强烈PD杂交，但它们的3D状态密度显示出明显的差异。最先进的第一原理计算表明，这些杂质状态如何介导特征的短距离交换相互作用，其强度敏感地随3D状态相对于费米水平的位置而变化。具有不同宿主化学计量的薄膜的测量支持这一趋势。我们的结果确定了杂质国家介导的交换相互作用在MTI磁性中的重要作用。
Since the discovery of the quantum anomalous Hall effect in the magnetically doped topological insulators (MTI) Cr:(Bi,Sb)$_2$Te$_3$ and V:(Bi,Sb)$_2$Te$_3$, the search for the exchange coupling mechanisms underlying the onset of ferromagnetism has been a central issue, and a variety of different scenarios have been put forward. By combining resonant photoemission, X-ray magnetic dichroism and multiplet ligand field theory, we determine the local electronic and magnetic configurations of V and Cr impurities in (Bi,Sb)$_2$Te$_3$. While strong pd hybridisation is found for both dopant types, their 3d densities of states show pronounced differences. State-of-the-art first-principles calculations show how these impurity states mediate characteristic short-range pd exchange interactions, whose strength sensitively varies with the position of the 3d states relative to the Fermi level. Measurements on films with varying host stoichiometry support this trend. Our results establish the essential role of impurity-state mediated exchange interactions in the magnetism of MTI.
