Li Qile, Trang Chi Xuan, Wu Weikang, Hwang Jinwoong, Cortie David, Medhekar Nikhil, Mo Sung-Kwan, Yang Shengyuan A, Edmonds Mark T
School of Physics and Astronomy, Monash University, Clayton, VIC, 3800, Australia.
ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, VIC, 3800, Australia.
Adv Mater. 2022 May;34(21):e2107520. doi: 10.1002/adma.202107520. Epub 2022 Mar 31.
Combining magnetism and nontrivial band topology gives rise to quantum anomalous Hall (QAH) insulators and exotic quantum phases such as the QAH effect where current flows without dissipation along quantized edge states. Inducing magnetic order in topological insulators via proximity to a magnetic material offers a promising pathway toward achieving the QAH effect at a high temperature for lossless transport applications. One promising architecture involves a sandwich structure comprising two single-septuple layers (1SL) of MnBi Te (a 2D ferromagnetic insulator) with ultrathin few quintuple layer (QL) Bi Te in the middle, and it is predicted to yield a robust QAH insulator phase with a large bandgap greater than 50 meV. Here, the growth of a 1SL MnBi Te /4QL Bi Te /1SL MnBi Te heterostructure via molecular beam epitaxy is demonstrated and the electronic structure probed using angle-resolved photoelectron spectroscopy. Strong hexagonally warped massive Dirac fermions and a bandgap of 75 ± 15 meV are observed. The magnetic origin of the gap is confirmed by the observation of the exchange-Rashba effect, as well as the vanishing bandgap above the Curie temperature, in agreement with density functional theory calculations. These findings provide insights into magnetic proximity effects in topological insulators and reveal a promising platform for realizing the QAH effect at elevated temperatures.
将磁性与非平凡能带拓扑相结合可产生量子反常霍尔（QAH）绝缘体和奇异量子相，例如量子反常霍尔效应，即电流沿量子化边缘态无耗散流动。通过与磁性材料接近在拓扑绝缘体中诱导磁序，为在高温下实现用于无损输运应用的量子反常霍尔效应提供了一条有前景的途径。一种有前景的结构是一种三明治结构，由两层MnBiTe（一种二维铁磁绝缘体）的单重七层（1SL）组成，中间夹着超薄的几层五层（QL）BiTe，预计会产生一种具有大于50meV的大能隙的稳健量子反常霍尔绝缘体相。在此，展示了通过分子束外延生长1SL MnBiTe / 4QL BiTe / 1SL MnBiTe异质结构，并使用角分辨光电子能谱探测其电子结构。观察到强六边形翘曲的大质量狄拉克费米子和75±15meV的能隙。通过观察交换- Rashba效应以及居里温度以上能隙的消失，证实了能隙的磁起源，这与密度泛函理论计算结果一致。这些发现为拓扑绝缘体中的磁近邻效应提供了见解，并揭示了一个在高温下实现量子反常霍尔效应的有前景的平台。
