Engineering of Topological Spin States in Epitaxial Alpha-Tin Layers

外延阿尔法锡层拓扑自旋态工程

• 批准号: 231119110
• 负责人: Privatdozent Dr. Jörg Schäfer
• 金额: --
• 依托单位: Lehrstuhl für Experimentelle Physik IV
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/231119110?language=en
• 关键词: Engineering; Topological; Spin; States; Epitaxial

This project is addressing a new type of topological insulator (TI) which has thus far only been proposed theoretically. It is formed by strained alpha-Sn grown epitaxially on a semi-conducting InSb substrate. The principal feasibility of this TI has recently been demonstrated by our group. The epitaxial approach opens various pathways to study the properties of the Dirac surface state, including different surface orientations of the TI crystal. Particular interest rests on the evolution of the nature of the Dirac bands as a function of layer thickness. The in situ preparation also allows to decorate the surface with an additional coating layer, specifically with heavy or magnetic atoms, which will alter the spin-orbit interaction at the TI interface and affect the properties of the Dirac state.The experimental approach to unveil the electronic properties is based on high-resolution angle-resolved photoemission (ARPES). This permits to track changes in the band dispersion with thickness, ranging from gapped Rashba-type states to the fully topological regime with a Dirac crossing. The Fermi level of the TI can be controlled precisely by doping, which allows to monitor the band situation and the Fermi surface even significantly above the Dirac point. The spin-topology will be addressed by using spin-resolved ARPES, where the evolution with thickness and under the influence of a surface coating can be unveiled. The studies are furthermore backed by collaboration partners in the field of density functional and many-body theory.

该项目正在研究一种新型的拓扑绝缘子(TI)，到目前为止，这种绝缘子还只是从理论上提出的。它是在半导体InSb衬底上外延生长的应变α-锡形成的。我们的团队最近已经证明了这种TI的主要可行性。外延方法为研究狄拉克表面态的性质开辟了多种途径，包括TI晶体的不同表面取向。特别令人感兴趣的是狄拉克带的性质作为层厚度的函数的演变。原位制备还允许在表面修饰一层额外的涂层，特别是重原子或磁性原子，这将改变TI界面的自旋-轨道相互作用，并影响Dirac态的性质。揭示电子性质的实验方法是基于高分辨率角度分辨光电子能谱(ARPES)。这使得可以跟踪带色散随厚度的变化，范围从有间隙的Rashba型态到具有狄拉克交叉的完全拓扑态。通过掺杂可以精确地控制TI的费米能级，这使得可以监测带的情况和费米表面，甚至远远高于狄拉克点。自旋拓扑将通过自旋分辨ARPES来解决，其中可以揭示随着厚度的变化和表面涂层影响下的演化。这些研究还得到了密度泛函和多体理论领域的合作伙伴的支持。