深紫外激光自旋分辨角分辨光电子能谱对Bi2Se3系列拓扑绝缘体薄膜的自旋电子结构研究及其自旋光控调制

Topological insulators represent a new quantum state of matter that are insulating in the bulk but metallic on the surface possessing unique electronic structure and spin texture. The Bi2Se3 series topological insulators are the prototypical topological insulators and attracted intensive investigations. In particular, when these topological insulator bulk materials are reduced to be 2-D or quasi 2D system, namely, topological insulatro films, they exhibite even more interesting topological physics including decoupling of topologiclal states，possible varaiation of the spin texture with films thickness etc.. In this preject, we proposed to directly probe and manipulate the unique spin texture of the topological insulator films by using the polarization-variable VUV laser-based spin- and angle-resolved photoemission spectroscopy(SARPES). Our research will mainly focus on: 1.The thickness dependent spin texture of the topological insulator films; 2. The newly theoretically proposed spin-orbital texture in the Bi2Se3 films by using polarization-variable laser light source. 3.Laser manipulation of the orbital-selective spin texture in these topological insulators and find potential applications for opto-spintronics technologies. We have sucessfully developed the VUV laser-based SARPES system. Thanks to the supper high flux (3 times better than that of new generation of synchrotron radiation light source ) together with the narrawer band width (0.26 meV), we are able to obtain a spin-resolved energy resolution of ~2.5 meV. To our knowledge, this is the best energy resolution achieved so far in the spin-resolved photoemission systems. The best angular resolution of our SARPES is around 0.3 degree; the momentum resolution is further improved due to the utilization of a low photon energy of the VUV laser (hv=6.994 eV). This state-of-art SARPES not only provide us with a unique opportunity to investigate the electronic structure and spin texture of topological insulators but also assure the sucessfully carrying out this project.

Bi2Se系列拓扑绝缘体是被广泛研究的典型拓扑绝缘体。而拓扑绝缘体的自旋电子结构，在实验上通过自旋分辨光电子能谱才能够实现直接的测量。本项目拟基于我们最新研制的基于偏振可调深紫外激光的自旋分辨角分辨光电子能谱系统，对Bi2Se3系列拓扑绝缘体薄膜的电子结构尤其是自旋结构开展系统和深入的研究,主要包括如下三个部分：1.研究Bi2Se3系列拓扑绝缘体薄膜的电子结构特别是自旋结构随膜厚的演变；2.研究Bi2Se3薄膜中最新发现的所谓自旋-轨道关联效应；3.研究利用深紫外激光的不同偏振模式实现对拓扑绝缘体薄膜自旋结构的调控，探索这一技术在未来光电自旋电子学（Opto-spintronics）技术中的潜在应用。我们的深紫外激光自旋分辨角分辨光电子能谱系统，其动量和能量分辨率都处于国际领先水平，为本项目的顺利实施提供了一个独特和理想的实验手段.