MnBi2Te4边态输运和磁性的空间分辨研究

Quantum anomalous Hall Effect (QAHE) is one of the important frontiers of condensed matter physics in recent years. The deep excavation in this field improves the understanding of the electronic structure, the growth and characterization of high-quality samples of the magnetic topological quantum materials, remarkably. Recently, the new discovered layered material MnBi2Te4, composed of single atomic sheets by each septuple-layer (SL), attracts great attention for its intrinsic magnetism, simple structure and great tunability. Within the septuple-layer the local moments are ferromagnetically coupled while inter-layer coupling is anti-ferromagnetic type, making the material hosting rich quantum effects, including the possible QAHE at higher temperatures, and more convenience on imaging the properties of its magnetic and edge state transport. Scanning Superconducting Quantum Interferometer (SQUID), imaging the spatial distribution of both the magnetization and the current simultaneously, is a powerful tool for studying such magnetic topological quantum system. With the help of scanning SQUID, the project will mainly focus on the MBE grown MnBi2Te4 film, the MnBi2Te4 flake made from single crystal cleavage, and the MnBi2Te4 heterogeneous structure, trying to reveal the difference between the magnetism and edge transport properties of such new material system and those of the traditional magnetic doping topological insulators. The effect of magnetic domain, defect, disorder and other factors on topological properties will be revealed experimentally, which provides valuable information for searching composites for better prototype materials and devices for application in the future.

量子反常霍尔效应（QAHE）是近年来凝聚态物理领域的重要前沿。对其深入的挖掘使磁性拓扑材料的电子结构研究、高质量样品的生长和表征都达到了前所未有的高度。近期发现的MnBi2Te4是一种新型的层状本征磁性拓扑绝缘体，层内具有铁磁性耦合，层间具有反铁磁性耦合，结构简单容易调控，蕴含丰富的量子效应，极有可能在较高温度实现QAHE, 有利于用复杂手段研究其性质。扫描超导量子干涉仪（SQUID），可以同时研究材料的磁性和边缘态输运性质的空间分布特性，是研究该材料体系的有力工具。本项目将主要用扫描SQUID分别研究MBE生长的MnBi2Te4薄膜、单晶解理的MnBi2Te4薄片、和MnBi2Te4异质结结构，揭示这种新型拓扑量子材料的磁性和边缘态输运性质与传统磁性掺杂拓扑绝缘体的区别，从实验上理解磁畴、缺陷、无序等因素对拓扑性质的影响，为寻找具有更好应用前景的复合材料提供有价值的线索。