拓扑电子材料由于受拓扑保护的电子态无背散射，所以材料迁移率较高、电阻极小、能耗极低，其应用将推动极低功耗新一代电子学器件的发展。目前尚无氧化物被实验证明是拓扑材料，氧化物对拓扑电子材料的应用和拓扑关联效应的研究非常重要。本项目首次发现氧化过程可调控的烧绿石结构Tl2Nb2O(6+x)是潜在的拓扑材料，拟利用第一性原理计算和低能有效模型分析来研究其拓扑电子态，为实验提供参考。拟研究:（1）调控O的含量来影响中心对称性，有望获得多种拓扑半金属;（2）利用压力来改变晶体对称性，有望获得Dirac半金属或者拓扑绝缘体;（3）利用过渡金属元素替换掺杂引入磁性及电子强关联效应，有望获得Weyl半金属或者量子反常霍尔绝缘体。该研究有助于理解氧化物出现拓扑的机制，阐明各种拓扑电子态间的相变机制和耦合关系。由于该系列材料可以制备出很好的单晶且氧化过程连续可调，这些理论预测极有可能得到实验验证。

Topological electronic materials have extremely low resistance, low dissipation, and high mobility, mainly because their electronic states are topological protected, which prevents various backscattering. Their applications will enable and boost the development of low-dissipation electronics devices. So far, no oxides are experimentally confirmed as topological materials. Moreover, studies of oxides for applications of topological electronic materials and investigation of correlated topological effect are of great importance. For the first time, our project discovers that a pyrochlore series Tl2Nb2O(6+x), which has tunable oxidation process, is a potential topological material. Using first-principles calculations and low-energy effective model analysis, we aim to study its topological electronic states and to provide guidance for experiments. We intend to study (1) impacting centro-symmetry by tuning the content of O, which probably results in diverse topological semi-metals, (2) changing crystal symmetry via pressure, which is promising to obtain Dirac semi-metals or topological insulators, (3) introducing magnetic properties and electron strong correlation effect into the system via substituting or doping transition metal elements, which is hopeful to obtain Weyl semi-metals or quantized anomalous Hall insulators. This study will not only be helpful to understand the mechanism of emerging topology of oxides, but also clarify the phase transition mechanism and coupling between various topological electronic states. Because good quality single crystal of this series material can be fabricated and the oxidation process is continuously adjustable, the theoretical prediction is promising to be confirmed by experiments.