Proximity-induced magnetism, electrodynamics, and impurites in topological insulators and Weyl semimetals

三维拓扑绝缘体（TI）和Weyl半金属（WS）由于其独特的性质和实验上的便利性，近年来引起了人们的极大兴趣. 最重要的是，它们可能在不同类型的异质结构中作为组成材料发挥重要作用。特别是，邻近效应对不同类型的有序介质，特别是磁性和超导材料，提供了一个途径，一些有趣的新的物理效应，可能会导致新的自旋为基础的电子元件的发展。我们的总体目标是更好地了解磁性和电子-电子相互作用在强三维拓扑绝缘体和Weyl半金属。有效的单粒子理论在预测这些系统的能带结构的主要特征方面是成功的，这是公认的。然而，越来越明显的是，多体效应产生不寻常的磁性是存在的，并可能发挥重要作用，我们的主要目标是研究磁化动力学，相变，自旋约瑟夫森效应由于邻近诱导的磁性（铁磁和反铁磁）对称性破缺异质结构，其中包括拓扑绝缘体和/或Weyl半金属。本论文的主要研究方向是最近在实验上实现的具有室温邻近感生磁性的双层和三层结构，进一步的目标是研究磁性和非磁性杂质的作用以及它们与TI和WS中表面态和体态的相互作用，从而得到电子波函数的非平凡准粒子干涉模式。特别强调的是，将放在可能的拓扑近藤绝缘体，SmB 6，和Weyl半金属的烧绿石带结构的时间反演对称性破缺的基础上的研究。

Due its unique properties three-dimensional topological insulators (TIs) and Weyl semimetals (WSs) have generated a lot of interest in recent years because of the combination of their peculiarproperties and experimental accessibility. Most importantly, they are likely to play a major role as component materials in different types of heterostructures. In particular, proximity effect to different types of ordered media, especially magnetic and superconducting materials, provides an avenue to several interesting novel physical effects that may lead to the development of new spin-based electronic components.Our overall goal is to better understand the magnetic properties and the electron-electron interaction in the strong three-dimensional topological insulators and Weyl semimetals. It is well established that effective one-particle theories are successful in predicting the main features of the band structure of these systems. Nevertheless, it becomes increasingly evident that many-body effects yielding unusual magnetic properties are present and could play an important role.Our main objective is to study magnetization dynamics, phase transitions, and spin Josephson effect due to proximity-inducedmagnetic (ferromagnetic and antiferromagnetic) symmetry breaking in heterostructures, which involve topological insulators and/or Weyl semimetal. The main focus willbe on bilayer and trilayer structures with room temperature proximity-induced magnetism, which have been recently realized experimentally.Our further goal is to investigate the role of magnetic and non-magnetic impurities and their interaction with surface and bulk states in TIs and WSs, resulting in the non-trivial quasiparticle intereference patterns of the electronic wave functions. The special emphasis will be put on the study of the presumably topological Kondo insulator, SmB6, and Weyl semimetals based on the pyrochlore band structure with broken time-reversal symmetry.