Construction and manipulation of topological insulators from III-V heterostructures

III-V 异质结构拓扑绝缘体的构建和操作

• 批准号: 530143959
• 负责人: Professor Dr. Sven Höfling
• 金额: --
• 依托单位: Lehrstuhl für Technische Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/530143959?language=en
• 关键词: Construction; manipulation; topological; insulators; III

Topological insulators (TIs) are new state of matter, characterized by an insulating bulk but gapless and counter-propagating surface or edge states. Among the vast amount of TI materials, composite quantum wells (QWs) heterostructures based on III-V materials, i.e., InAs/GaSb, provide unprecedented device functionality in combination with the advanced epitaxial and device fabrication routines of III-V semiconductors. These composite QW heterostructures are particularly attractive two-dimensional (2D) TIs thanks to their rich phase diagram accessible by band and symmetry engineering and by the application of external electric fields, allowing the modification of their properties with unique flexibility. However, despite many investigations, a fully convincing demonstration of helical edge states in the topological insulating phase in this material system is still elusive. This project therefore proposes first to overcome the main obstacles to the observation of the so-called quantum spin Hall effect (QSHE) in these materials, such as the small energy gap inherent in these asymmetric structures. Moreover, since the discovery of 2D TIs, a large variety of three-dimensional (3D) TIs and semi metallic (SM) states have also been identified in different condensed matter systems. However, the materials in which these topological states have been observed do not allow any continuous tunability of their band structure or topological properties. Therefore, a flexible platform with many adjustable parameters is still very much in demand, both to better probe their physical properties and to consider practical applications. By controlling crystal symmetries and multiple band inversions in InAs/GaSb-based superlattices, it becomes possible to create all known topological quantum states such as 3D TIs, Dirac and Weyl SMs, but also so-called higher order TIs (HOTIs) with a phase diagram of unprecedented richness. Unlike the "lower order" case, edge states of HOTIs are at least two dimensions smaller than that of the system. The project therefore aims on the one hand to create a flexible platform for the study of 2D and 3D topological states based on QWs and III-V superlattices and on the other hand to evidence and control the QSHE in structures of optimized growth and technological processes. The first objective is the realization of a technological breakthrough: the control of dual gated high-performance field effect devices, allowing the observation of the trivial-to-topological phase transition by external voltage rather than structural change. The second objective is to observe quantized conduction of edge states in three-layer QW structures. The third objective is to validate various topological states existing in 3D InAs/Ga(In)Sb superlattices, such as 3D TIs, Dirac and Weyl SMs, and 3D HOTIs.

拓扑绝缘体（TI）是一种新的物质状态，其特征是绝缘体，但无间隙和反向传播的表面或边缘状态。在大量的TI材料中，基于III-V族材料的复合量子威尔斯（QW）异质结构，即，InAs/GaSb与III-V族半导体的先进外延和器件制造程序相结合，提供了前所未有的器件功能。这些复合量子阱异质结构是特别有吸引力的二维（2D）TI由于其丰富的相图可通过带和对称性工程和外部电场的应用，允许修改其属性具有独特的灵活性。然而，尽管许多调查，一个完全令人信服的演示螺旋边缘状态的拓扑绝缘相在这个材料系统仍然是难以捉摸的。因此，该项目首先提出克服在这些材料中观察所谓的量子自旋霍尔效应（QSHE）的主要障碍，例如这些非对称结构中固有的小能隙。此外，自从2D TI的发现，大量的三维（3D）TI和半金属（SM）状态也被确定在不同的凝聚态系统。然而，这些拓扑状态已被观察到的材料不允许任何连续的可调谐性，其能带结构或拓扑性质。因此，仍然非常需要具有许多可调参数的柔性平台，以更好地探测其物理特性并考虑实际应用。通过控制InAs/GaSb基超晶格中的晶体对称性和多能带反转，可以创建所有已知的拓扑量子态，例如3D TI，Dirac和Weyl SM，以及所谓的高阶TI（HOTI），具有前所未有的丰富相图。与“低阶”情况不同，HOTI的边缘态至少比系统的边缘态小两个维度。因此，该项目的目标是一方面为基于QW和III-V族超晶格的2D和3D拓扑状态的研究创建一个灵活的平台，另一方面在优化生长和技术过程的结构中证明和控制QSHE。第一个目标是实现技术突破：控制双栅高性能场效应器件，允许通过外部电压而不是结构变化观察平凡到拓扑的相变。第二个目标是观察三层量子阱结构中边缘态的量子化导电。第三个目标是验证三维InAs/Ga（In）Sb超晶格中存在的各种拓扑态，如三维TI，Dirac和Weyl SM，以及三维HOTI。