Pournaghavi Nezhat, Sadhukhan Banasree, Delin Anna
Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, AlbaNova University Center, SE-10691, Stockholm, Sweden.
Department of Physics and Astronomy, Uppsala University, 516, SE-75120, Uppsala, Sweden.
Sci Rep. 2025 Jan 17;15(1):2255. doi: 10.1038/s41598-024-80694-7.
Non-trivial band topology along with magnetism leads to different novel quantum phases. When time-reversal symmetry is broken in three-dimensional topological insulators (TIs) through, e.g., the proximity effect, different phases such as the quantum Hall phase or the quantum anomalous Hall(QAH) phase emerge, displaying interesting transport properties for spintronic applications. The QAH phase displays sidewall chiral edge states, which leads to the QAH effect. We have considered a heterostructure consisting of a TI, namely Bi[Formula: see text]Se[Formula: see text], sandwiched between two two-dimensional ferromagnetic monolayers of CrI[Formula: see text], to study how its topological and transport properties change due to the proximity effect. Combining DFT and tight-binding calculations, along with non-equilibrium Green's function formalism, we show that a well-defined exchange gap appears in the band structure in which spin-polarised edge states flow. In a finite slab, the nature of the surface states depends on both the cross-section and thickness of the system. Therefore, we also study the width and finite-size effects on the transmission and topological properties of this magnetised TI nanoribbon.
非平凡能带拓扑结构与磁性一起会导致不同的新型量子相。当三维拓扑绝缘体（TI）中的时间反演对称性通过例如近邻效应被打破时，会出现不同的相，如量子霍尔相或量子反常霍尔（QAH）相，展现出对自旋电子学应用而言有趣的输运特性。QAH相呈现侧壁手性边缘态，这导致了QAH效应。我们考虑了一种异质结构，它由夹在两个二维CrI[公式：见原文]铁磁单层之间的TI（即Bi[公式：见原文]Se[公式：见原文]）组成，以研究其拓扑和输运性质如何因近邻效应而改变。结合密度泛函理论（DFT）和紧束缚计算以及非平衡格林函数形式，我们表明在能带结构中出现了一个明确的交换能隙，其中自旋极化边缘态在其中流动。在有限平板中，表面态的性质取决于系统的横截面和厚度。因此，我们还研究了宽度和有限尺寸对这种磁化TI纳米带的传输和拓扑性质的影响。
