大能隙量子自旋霍尔效应薄膜研究

Quantum spin hall (QSH) system is a novel type of two dimensional insulators or semiconductors. In QSH system, there exists one dimensional metallic edge state protected by time reversal symmetry, while its bulk states have an energy gap. Electrons in the one dimensional edge state can be used for the dissipationless electric conduction and pure spin current. QSH has been proposed to be very useful for the future electronics and spintronics. However, the possible application of QSH is limited by the very small (~ meV) two dimensional bulk energy gap. The key question in this field is how to realize QSH in large gap materials. Based on our previous results, in this project, we propose to study the growth of QSH films with the large energy gap (single layer Bi and Stanene) on the insulating substrates and how to in situ control its electronic structures by combining synchrotron radiation (Hefei) based angle-resolve photoemission spectroscopy and the molecular beam epitaxy technique. Our goal is to realize the QSH films with large energy that can be used for the study of electric transport measurements. We plan to explore the possibility of realizing QSH effect in the films with large energy by the transport measurements.

量子自旋霍尔效应体系是一类特殊的二维绝缘体（或半导体）材料。该体系体内电子有能隙，在一维边缘存在受时间反演对称性保护的导电通道。一维边缘态中的电子可用于实现无耗散电子输运和纯自旋流产生，在未来低能耗电子学和自旋电子学方面有重要的潜在应用价值。受限于现有材料的微小二维体能隙（几个毫电子伏），量子自旋霍尔效应的实际应用面临巨大障碍。急需解决的关键科学问题是如何在实验上实现大能隙的量子自旋霍尔效应材料。基于前期研究基础，本项目提出，利用合肥同步辐射角分辨光电子能谱结合分子束外延技术研究在绝缘基底上大能隙量子自旋霍尔效应薄膜（主要针对单层铋和锡烯薄膜）的制备和电子态调控，实现可用于量子自旋霍尔效应电输运特性研究的大能隙薄膜材料。在此基础上，开展电子输运特性研究，探索大能隙材料中量子自旋霍尔效应态实现的可行性。

拓扑量子态材料因为其特殊的电子能带结构在未来电子学和信息学方面有重要的潜在应用价值。量子自旋霍尔效应绝缘体，也统称为二维拓扑绝缘体是其中一类二维体系。寻找和调控新的二维拓扑绝缘体以及其他拓扑量子材料是该领域重要的科学问题。本项目针对这个科学问题，利用分子束外延和晶体生长等样品制备方法，利用同步辐射角分辨光电子能谱结合其他实验测量手段，在第一性原理计算的帮助下，针对拓扑材料开展了一系列的研究。取得了如下进展：1）实现了两种适用于大能隙二维拓扑绝缘体锡烯薄膜生长的绝缘体基底---氯化钠结构SrTe(111)薄膜以及In掺杂无金属表面态的Bi2Te3；2）理论上发现利用氢原子和卤素原子修饰可将As(110)和Sb(110)薄膜转变为大能隙二维拓扑绝缘体；3）在超导基底上制备出二维拓扑绝缘体铋薄膜，并观察到了一维边缘态和超导态共存；4）在单层FeSe薄膜中发现反铁磁长程序，支持其为一种二维拓扑超导体；5）发展出一种基于紫外光氧化刻蚀的微纳加工新方法，利用该方法能够在超薄的三维拓扑绝缘体薄膜中实现受控的氧化绝缘。通过上述工作，促进了对二维拓扑绝缘体以及相关拓扑材料的研究发展。本项目在Phys. Rev. Lett.、Phys. Rev. B、Nat. Communs.、Nano Lett.、Appl. Rev. Lett.、Chin. Phys. B等杂志上共发表29篇论文，申请发明专利1项、培养毕业博士生6名，硕士生2名。