Tailoring the band structure of thin films by strain and by the growth of artificial heterostructures

材料的电子能带结构决定了其电子、光学、磁性和催化性能，因此能带结构的精确调节对于广泛的应用具有根本的重要性。这就需要全面了解能带结构与原子构成的关系。调整薄膜能带结构的两种可能的方法是人工异质结构的生长和施加机械应变。特别是，应变被认为是一个强大的工具，因为，在材料的弹性范围内，它承担着电子能带结构的可逆原位工程的潜力，从而材料的功能特性。通过在单轴拉伸测试过程中进行角分辨光电子能谱，我们希望建立拓扑绝缘体的能带结构上的应变的效果，拓扑晶体绝缘体和过渡金属二硫属化物。结合被拘留的表征的微观结构和薄膜的应力状态，这将使系统的量化的影响的应变和破坏晶体对称性的能带结构，并铺平了道路，使用应变作为原位工具定制的能带结构。此外，我们计划研究超导体和拓扑绝缘体之间的邻近效应。通过进行角分辨光电子能谱，我们将建立邻近诱导超导的拓扑表面状态和体带的拓扑绝缘体膜的厚度以及温度的函数，揭示的机制和邻近诱导超导的决定性因素。

The electronic band structure of a material determines its electronic, optical, magnetic and catalytic properties and thus a precise adjustment of the band structure is of fundamental importance for a wide range of applications. This requires a comprehensive understanding of the correlation of the band structure with the atomic constitution. Two possible ways to tailor the band structure of thin films are the growth of artificial heterostructures and the imposing of a mechanical strain. In particular, strain is considered as a powerful tool, since, within the elastic regime of the material, it bears the potential for a reversible in-situ engineering of the electronic band structure and thus the functional properties of the material.By performing angle-resolved photoemission spectroscopy during uniaxial tensile testing of ultrathin films, we want to establish the effect of strain on the band structure of topological insulators, topological crystalline insulators and transition metal dichalcogenides. In combination with a detained characterization of the microstructure and the stress state of the thin films, this will enable a systematic quantification of the effect of strain and of breaking the crystal symmetry on the band structure and pave the way to use strain as an in-situ tool for tailoring the band structure. Furthermore, we plan to investigate the proximity effect between a superconductor and a topological insulator. By performing angle-resolved photoemission spectroscopy, we will establish the proximity-induced superconductivity in the topological surface state and the bulk bands as functions of the topological insulator film thickness as well as the temperature, shedding light on the mechanism and the decisive factors for the proximity-induced superconductivity.