拓扑表面态新奇自旋构形的自旋极化扫描隧道谱研究

The surface state of topological insulators has unique spin characters, which is the basis for many novel topological quantum phenomena.To date, the studies on the spin properties of topological surface state have been mainly focused on its momentum space with spin and angle resolved photo emission spectroscopy. And its study in real space is still lacking. In this project, we will use spin-polarized scanning tunneling microscopy, which is a probe that is spin sensitive in real space, to investigate the novel quantum spin phenomena of topological surface state, which are expected to emerge in real space under certain external perturbations. We will systematically investigate the novel spin textures that are generated by the influence of an impurity potential on the Landau wave functions of topological surface state in Bi2Se3.The study could unravel the spin character in the Landau wave function of topological surface state. We will also investigate the magnetic domain structure and chiral edge modes that are existing in Cr doped magnetic topological insulator Sb2Te3, and clarify the underlying mechanism that mediates the magnetic interaction. The execution of this project will on one hand enrich our understanding of the spin properties of topological surface state, set a foundation for exploring yet more exotic topological phenomena, and on the other hand open a new platform for the application of topological insulators in spin-based electronics.

拓扑绝缘体表面态具有独特的自旋特性，是许多新奇拓扑量子物理现象的基础。目前对拓扑表面态自旋的研究主要借助于自旋和角度分辨的光电子能谱在动量空间展开，但是在实空间的研究尚属空白。在本项目中，我们将利用自旋极化扫描隧道显微镜这种对自旋灵敏的实空间表征工具，研究拓扑表面态在特定外界作用下在实空间预期出现的新奇自旋量子现象。这包括系统研究拓扑绝缘体Bi2Se3中的朗道波函数在杂质电势调控下产生的新奇自旋构形，以揭示拓扑表面态朗道波函数的自旋特性；探测Cr掺杂的磁性拓扑绝缘体Sb2Te3表面态中的磁畴结构和手性边界态，并澄清其中的磁性相互作用机制。该项目的实施将一方面丰富我们对拓扑表面态自旋特性的理解，为实现更加新奇的拓扑物理现象奠定基础，另一方面将为拓扑绝缘体在自旋电子学中的应用开辟新的平台。

拓扑绝缘体在表面或边界处存在受体能带拓扑特性保护的表面态或边界态。这种拓扑表面态具备特殊的自旋结构和物理性质，并可以为验证体系的拓扑性质提供重要依据。本项目的研究内容是揭示与拓扑表面态的自旋属性相关的物理性质，并探索新的拓扑绝缘体体系。主要成果包括：（1）我们利用实空间三维扫描隧道谱，观测到拓扑表面态朗道能级的塞曼效应，并发展了一套处理表面电势干扰的处理方法，精确测量到了两种拓扑表面态的不同兰德因子。（2）我们还通过实空间扫描隧道谱，观测到了1T’结构的WTe2台阶处存在拓扑边界态，验证理论上的预测。为发展拓扑电子学器件奠定了材料基础。另外，还系统研究了不同厚度的Bi薄膜的拓扑性质，澄清了长期以来存在的争议。

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