电场和掺杂对拓扑晶态绝缘体SnTe薄膜电子结构和磁性的影响

Recent discoveries of novel structural and electronic states and the latest realization of a new type of topological order in SnTe have reinvigorated strong interest in this fascinating material. Theoretical workers identified tin telluride (SnTe) as a distinct type of topological crystalline insulator (TCI), in which the metallic surface states are protected by the mirror symmetry of the crystal, in contrast to the time-reversal symmetry protection in the earlier identified Z2 topological insulators. It has been a topic of great interest because of its fundamental physics and potential applications in electronic devices. While, the narrow band gap of SnTe is very sensitive to changes of external conditions such as pressure, electric field, temperature or doping. The mechanism of topological states and magnetism from doping impurities is unclear. In this project, the first-principles methods within the framework of density functional theory would be used to systematically investigate the influence of doping and electric field on the surface electronic structure and magnetism of SnTe films. The research results will be contribute to understand the mechanism of topological states and magnetism from the electric field and doping impurities and search for the doping impurities and the condition of electric field which can manipulation effectively electronic structure. It is expected that the research conclusions can provide a theoretical guidance for the practical application of topological crystalline insulator SnTe film materials in electronic devices.

最近的理论和实验研究发现碲化锡是一种新型拓扑绝缘体，被称为“拓扑晶态绝缘体”，其表面的金属态由晶格反演对称性所保护，与之前的 Z2型拓扑绝缘体不同（表面的金属态由时间反演对称性保护）。因为SnTe在基础物理学和电子器件应用等方面具有重要意义，它的出现迅速受到人们的广泛关注。然而窄带隙的碲化锡其带隙值随温度、电场和压强等条件的变化而变化，这些不确定因素阻碍了人们对其物理性质的进一步探索，同时SnTe拓扑表面态对掺杂也非常敏感，而掺杂对其拓扑性质和磁性的作用机理尚不清楚。本项目将运用第一性原理方法系统研究电场和掺杂对拓扑晶态绝缘体SnTe薄膜电子结构及磁性的影响，深入了解电场和掺杂对SnTe薄膜拓扑性质、电子结构和磁性影响的作用机理，探寻能实现其电子结构有效调控的掺杂物质和电场条件，以期为基于拓扑薄膜材料的电子器件的制备、设计和调控等相关实验研究提供理论参考。

基于拓扑材料器件在基本电子学、量子自旋、热电材料等方面的广阔应用前景，我们对目前普遍关注的重要的拓扑晶态绝缘体以及二维材料和器件的基本特性进行了系统的研究。我们主要探究了自旋轨道耦合效应及应变效应下SnTe电子结构的变化，并通过掺杂过渡金属原子对其调控，得到了较为理想的结果。我们发现本征块状SnTe材料具有窄间隙半导体特性且表现出非磁性基态，然而在Mn取代的中心对称构型中，体系磁性被诱导且费米能级附近出现谐振态。当对掺杂体系施以0-6％的压缩应变时，TCI特性仍被保持，体系电子结构发生明显变化，表现出n-p-n转换，这将有利于提高Seebeck系数，拓展了其在热电材料领域及磁性器件的潜在应用。另外，我们也关注了相关的二维材料器件并探究了3d过渡金属原子掺杂的MoS2, WS2, WSe2, ZrS2单层、过渡金属和贵金属Ni、 Pd、Pt掺杂的WS2薄膜、应变下Cr掺杂的HfS2薄膜、V族和VII族原子掺杂的HfS2, ZrS2, MoSe2单层。Mn原子与N原子共掺杂的 ZrS2薄膜以及掺杂效应的氢化MoSe2与ZrSe2纳米带，通过分析体系的能带结构、电导率类型、磁矩、电荷密度，结果均显示出有效的磁性诱导及半导体、金属、半金属间的转变，极大丰富了电子自旋器件种类。同时我们也研究了电场作用下异质结电子结构和光学性质，发现基于这些材料的纳米薄膜、纳米带及异质结在未来电子学、自旋电子学、光电子学中的潜在应用并为微纳米材料和器件的制备提供了相关理论依据。

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