基于二维锑烯范德瓦尔斯异质结的高温非狄拉克陈绝缘体

Considering the demands of high-temperature Chern insulators that are easy to synthesize in experiment and apply in practice, research with respect to the physical properties and mechanism of Van der Waals heterostures constituting of antimonene and two-dimensional ferromagnetic insulators (the recently experimentally synthesized materials such as Crl3, Cr2Ge2Te6, VSe2 and MnSe2) will be conducted. The followings will be the main content of the research. First, by exploiting the non-Dirac dispersion of antimonene and constructing Van der Waals heterostructures, the difficulties in experiments of Chern insulator would be solved, such as low Curie temperature, weak exchange field, reconstruction of substrate, and magnetic domains. By analyzing structure stability, electromagnetic properties and topological properties of the heterostructures constructed above, stable non-Dirac Chern insulators with large band gaps are likely to be found. Second, by analyzing the influence and mechanism of various effects (such as SOC and Van der Waals interaction) in the system and combining symmetry analysis, an effective model of the system will be constructed, which will illustrate the physical mechanism behind such kind of Chern insulators and give general principles to construct non-Dirac Chern insulators. Third, the edge state transporting properties of such Chern insulators and their behaviors under strain and electric filed will be studied. Plan for designing new quantum low-dissipation functional devices based on such heterostructures will be proposed during this process. This interdiscipline research (computational physics, condensed matter theory and material science) will provide the theoretical basis of high-temperature Van der Waals non-Dirac Chern insulator and further guide its experimental realization and application.

面向易制备且易应用的高温陈绝缘体的需求，针对由锑烯和二维铁磁绝缘体（如实验已制备的CrI3、Cr2Ge2Te6、VSe2、MnSe2）所构成的范德瓦尔斯异质结的物理性质及机制展开研究。主要包括：（1）利用锑烯的非狄拉克能带并结合构建异质结的方法，来解决陈绝缘体实验中所面临的低铁磁居里温度、弱交换场、衬底截断面再构、磁畴等问题，通过分析各异质结构型的稳定性、电学、磁学及拓扑性质，以期实现有较大体能隙的非狄拉克陈绝缘体；（2）研究此类陈绝缘体中各种作用的效果与机制，结合对称性分析，建立体系的低能有效模型，给出实现此类陈绝缘体的一般性的指导方法；（3）研究此类陈绝缘体边界态的输运特性，并尝试利用应力、电场等手段进行调控，规整出基于此类异质结的低耗散量子功能器件的设计方案。本研究体现了计算物理学、凝聚态理论和材料等多学科的交叉，为高温条件下的范德瓦尔斯型非狄拉克陈绝缘体的实现及应用提供理论支持。

在本青年科学基金项目的有力支持下，我们运用第一性原理计算与对称性分析以及低能有效模型相结合的方法，围绕着二维量子材料的新奇物性展开研究，主要取得了以下三个方面的研究成果：一、拓扑半金属的研究。我们在具有螺旋对称性的二维磁性系统中提出了二维半陈-外尔半金属相（2D half Chern-Weyl semimetal）。这是一种二维磁性外尔半金属相和半陈绝缘相互相绑定的新奇拓扑相，其中通过改变系统的磁矩方向，可以实现两种绑定的拓扑相的切换。进一步，我们预言了在单层TiTe薄膜中可以实现这种新奇拓扑相。二、高阶拓扑物态的研究。我们提出了利用规则孔洞修饰的一般化方法，可以将二维狄拉克材料转换为高阶拓扑绝缘体。这个方案可以极大地拓展二维高阶拓扑绝缘体地材料实现方案。三、谷电子学的研究。我们提出并实现了具有大的谷极化效应的半谷材料（half-valley）MBr2薄膜（其中M为Ru或者Os元素），并在这类材料中进一步发现了边界态的“手性-自旋-谷”锁定效应。