拓扑绝缘体中体态与边界态相互影响的机制及其调控

Topological insulators are a category of materials with electronic topological order. What make them intriguing are their boundary states. Boundary states within the bulk gap are protected by topology and symmetries, therefore robust against perturbations such as disorder and interactions. This gives rise to a high performance of quantum transport. Nevertheless, boundary states cannot exist independently: they are determined by the topological properties of bulk bands and are grown from the bulk bands. In the experimentally realized three-dimensional topological insulators so far, there are strong mixings and scatterings between the bulk states and boundary states, which make the robustness of boundary states unachievable. In this project, we will perform systematic and theoretical investigations on the interplay between the bulk and boundary states due to impurities, external fields and many-body interactions: the control of bulk and boundary states, and the scattering between bulk and boundary states. This project is aiming at offering theoretical proposals to minimize the impacts from bulk states and to maximize the effects from boundary states in realistic materials. The results will be beneficial for the experimental realizations and technical applications of topological materials.

拓扑绝缘体是一类具有拓扑序电子态的材料。它真正让人们感兴趣的是边界态。在体带隙内的边界态具有被拓扑和对称性保护的稳定性，对微扰（例如无序和多体互作用）不敏感，因此具有极强的量子输运能力。然而，边界态是由体能带的拓扑性质决定的，也是从体能带里生长出来的，原则上就不能独立存在。目前实验上发现的三维拓扑绝缘体中，体态和表面态之间就具有很强的混合与散射，导致表面态的优良性质很难体现。本项目将对体态和表面态的相互影响进行系统和深入的理论研究，主要是探索和理解以下问题的物理机制：外场、杂质和多体互作用对体态和边界态的调控，以及它们对体态和边界态之间散射的影响。研究目标是为在真实材料中消除体态影响，最大程度地体现边界态的优良性质提供理论依据。研究结果对拓扑材料的实验实现和技术应用具有指导作用。

我们利用各种理论方法，广泛研究了二维和三维拓扑材料中体态和边态的相互影响，取得了一系列研究结果，完成了研究计划。成果包括：石墨烯-硅烯异质结中的谷极化输运，二维拓扑绝缘体中体态和边缘态的相互影响及其调控，体维度和边缘维度对于边缘态输运的影响，高陈数量子反常霍尔态的局域化过程；系统研究了三维拓扑半金属中体态的势垒隧穿效应；超导-硅烯异质结中高效的交叉Andreev反射及其成因。在本项目的资助下，共完成8篇学术论文，其中6篇已在国际期刊发表，2篇已投稿。在1次国际会议做邀请报告。培养博士后2人，博士生1人。