Transport properties of bilayer topological insulators

双层拓扑绝缘体的输运特性

• 批准号: 237750603
• 负责人: Professor Dr. Björn Trauzettel
• 金额: --
• 依托单位: Institut für Theoretische Physik und Astrophysik
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/237750603?language=en
• 关键词: Transport; properties; bilayer; topological; insulators

In two spatial dimensions (2D), time-reversal symmetric topological insulators (TI) are called quantum spin Hall (QSH) insulators. They are characterized by a gap in the bulk band structure and peculiar helical edge states at the physical boundaries of QSH systems. Realizations of these systems have been achieved on the basis of Hg(Cd)Te and InAs/GaSb quantum wells. In fact, the 2D electron gas (2DEG), in these quantum well structures, can be in three distinct regimes: (i) TI regime; (ii) normal band insulator regime; and (iii) Dirac semimetal regime where conduction and valence band touch each other.Novel physics arises if two QSH systems are combined in a bilayer structure. Then, the two 2DEGs (of the two layers) can interact with each other in different ways, for instance, via tunneling processes or Coulomb interaction. It is interesting to study the fate of the bilayer topological phases. In fact, the bilayer scenario offers totally new possibilities of generating topological insulating phases, e.g. through the formation of an exciton condensate.In this project, we want to study transport properties of bilayer topological insulators. This analysis should be done, under physical conditions, where the two layers interact with each other solely via Coulomb interaction. One of the key issues, we would like to address, is the imprint of the topological phases within each layer on the interlayer transport properties. To do so, we will calculate the Coulomb drag problem in these bilayer structures, i.e. the current response in layer 2 if a voltage is applied to layer 1. Interestingly, depending on the topological phases of the constituents, this problem requires us to consider a coupling between two 1D helical edge states, two 2DEGs, or even a coupling between a 1D helical edge state (in one layer) and a 2DEG (in the other layer). Evidently, rich transport physics can emerge in these bilayer systems and we expect that it helps us to better understand the interplay of Coulomb interaction and topological insulating phases of matter. Particularly, we want to make observable predictions that characterize the co-existence of interaction effects and topological order in bilayer systems.

在二维空间（2D）中，时间反转对称拓扑绝缘体（TI）被称为量子自旋霍尔（QSH）绝缘体。它们的特点是体能带结构中存在间隙，以及 QSH 系统物理边界处的特殊螺旋边缘态。这些系统的实现是基于 Hg(Cd)Te 和 InAs/GaSb 量子阱。事实上，在这些量子阱结构中，二维电子气 (2DEG) 可以处于三种不同的状态：(i) TI 状态； (ii) 正常带绝缘体状态； (iii) 狄拉克半金属体系，其中导带和价带相互接触。如果两个 QSH 系统组合成双层结构，就会出现新的物理现象。然后，两个 2DEG（两层）可以以不同的方式相互作用，例如通过隧道过程或库仑相互作用。研究双层拓扑相的命运很有趣。事实上，双层方案提供了生成拓扑绝缘相的全新可能性，例如通过形成激子凝聚体。在这个项目中，我们想要研究双层拓扑绝缘体的输运特性。该分析应该在物理条件下进行，其中两层仅通过库仑相互作用相互作用。我们想要解决的关键问题之一是每层内的拓扑相对层间传输属性的影响。为此，我们将计算这些双层结构中的库仑阻力问题，即如果向第 1 层施加电压，第 2 层中的电流响应。有趣的是，根据成分的拓扑相，这个问题需要我们考虑两个 1D 螺旋边缘态、两个 2DEG 之间的耦合，甚至 1D 螺旋边缘态（在一层中）和 2DEG（在另一层中）之间的耦合。显然，这些双层系统中可以出现丰富的输运物理学，我们期望它有助于我们更好地理解库仑相互作用和物质拓扑绝缘相的相互作用。特别是，我们希望做出可观察的预测来表征双层系统中相互作用效应和拓扑顺序的共存。