负自旋轨道耦合拓扑绝缘体的第一性原理研究

Topological insulator (TI) is a novel quantum material state characterized by the non-trivial topological order. It behaves as an insulator in the bulk, while possesses a gapless Dirac-type metallic surface state. The spin-orbit coupling (SOC) plays important roles in generating topologically nontrivial band structure. Topological insulator would exhibit many interesting properties after considering negative SOC. The objectives of the project include three points. (1) We will search or design a family of TI with negative SOC and investigating their novel topological quantum state. So far, the SOC of most TI materials are positive. This project will greatly expend the scope of TI materials. (2) We will Search for novel topological quantum state and interesting electronic properties by tuning the strength and sign of SOC. We also study heterostructures of TI with different SOC, to search for more fascinating quantum phenomena. (3) We will develop a set of codes to calculate the topological invariants, and combine the code with first-principles software. Based on this program, we can do further studies including non-equilibrium transport and strongly correlated calculations in the future.

拓扑绝缘体是一类具有拓扑非平庸性质的新型量子物质态，其内部绝缘，但存在无能隙的狄拉克型的表面金属态。自旋轨道耦合对拓扑非平庸的电子结构有着重要的影响。考虑负自旋轨道耦合以后，拓扑绝缘体将表现出许多新奇的物理性质。本项目的研究目标是：（1）寻找和设计一系列负自旋轨道耦合的拓扑绝缘体材料。目前为止，人们发现的拓扑绝缘体材料的自旋轨道耦合都是正的，本项目将预言一类全新的自旋轨道耦合为负的拓扑绝缘体材料，从而大大拓展拓扑绝缘体的材料种类。（2）调节自旋轨道耦合的强度和符号，以设计和优化拓扑材料的电子结构，从而寻找新的拓扑量子态。同时研究把不同自旋轨道耦合的拓扑材料做成异质结，以观察更多新奇有趣的物理现象。（3）发展一套计算拓扑不变量的程序，并实现在第一性原理程序中的嵌入。基于这套程序我们将来可以向非平衡输运和强关联材料计算方面做进一步的发展。

拓扑绝缘体是一类具有拓扑非平庸性质的新型量子物质态，其内部绝缘，但存在无能隙的 狄拉克型的表面金属态。自旋轨道耦合对拓扑非平庸的电子结构有着重要的影响。考虑负自旋轨道耦合以后，拓扑绝缘体将表现出许多新奇的物理性质。本项目完成的的研究内容:(1)寻找和设计了一类负自旋轨道耦合的拓扑绝缘体Cu2S系列材料。(2)开展了关于拓扑绝缘体/半金属相变研究，探索了二次型能带交叉点的拓扑性质。(3)发展了一套计算拓扑不变量的程序，并初步实现了在第一性原理程序中的嵌入。基于这套程序我们将来可以向非平衡输运和强关联材料计算方面做进一步的发展。