两类具有电子关联的拓扑晶体的生长及物理性能研究

Topological surface state is a novel quantum state, which possesses gapless surface state. Because surface state is spin-polarized， which is protected by time-reversal symmetry. It makes topological materials quite promising at future applications, such as spintronics and quantum computing. The recent theoretical works predict that topological insulators can be found not only in single-electron semiconductor systems, but also in correlated-electron systems. Kondo insulators (SmB6 , YbB6) and ferromagnetic semimetal (HgCr2Se4) were predicted to have topological surface state. But there is no experimental proofs. This project plans to grow SmB6,YbB6 and HgCr2Se4 crystals by the floating zone, flux and vapor phase transport methods. We design some systems (such as mixed crysral growth, doping and adjust stochiometry) to control Fermi level, and characterize their topological nontrival surface state. Combining angle-resolved photoemission spectroscopy and transport propoerties measurement characterize their surface states. Conducting this project will deepen our understanding of topological state in correlated-electron systems.

拓扑表面态是一种全新量子态，表面是无能隙金属性，其无能隙表面态是受时间反演对称性所保护的具有自旋分辨的电子态，在未来的自旋电子学和量子计算领域有重要的应用前景。理论预言除了在单电子体系半导体晶体中存在拓扑表面态外，也可能存在于强电子关联的体系中。已有理论计算预言了电子关联近藤绝缘体SmB6，YbB6晶体和铁磁性半金属HgCr2Se4晶体存在拓扑表面态，但尚未有实验证实。本项目拟用光学浮区法、助熔剂法和气相输运法生长具有电子关联的拓扑晶体。通过生长条件和组分的控制（混晶，元素的掺杂及化学计量比）调节费米面位置，以求实验证实这两类材料具有的非平庸拓扑表面态。综合利用角分辨光电子能谱、电(磁)输运揭示这两类晶体的表面态。本项目的实施将加深对电子关联体系拓扑性的理解。

拓扑表面态是一种全新量子态，表面是无能隙金属性，其无能隙表面态是受时间反演对称性所保护的具有自旋分辨的电子态，在未来的自旋电子学和量子计算领域有重要的应用前景。理论预言除了在单电子体系半导体晶体中存在拓扑表面态外，也可能存在于强电子关联的体系中。已有理论计算预言了电子关联近藤绝缘体 SmB6，Zr/HfTe5, Mo/WTe2等晶体存在拓扑表面态，但尚未有实验证实。本项目采用光学浮区法、助熔剂法和气相输运法生长具有电子关联的拓扑晶体。通过生长条件和组分的控制（混晶，元素的掺杂及化学计量比）调节费米面位置，以求实验证实这两类材料具有的非平庸拓扑表面态。综合利用角分辨光电子能谱、电(磁)输运揭示这两类晶体的表面态。本项目的实施将加深对电子关联体系拓扑性的理解。