Topological Insulators: A study of bulk crystalline and Nanomaterials

拓扑绝缘体是一类具有拓扑表面态的量子材料。这些材料通常是小带隙半导体，其中大部分材料是绝缘的，但它们表现出特殊的表面状态，具有导电性和拓扑保护。这些材料通常是由重原子构成的，这些重原子会产生强烈的自旋轨道耦合，从而形成不会被散射或杂质破坏的表面态。它被证明是研究凝聚态物理的理想材料，因为这些材料的物理学是新颖的，它们为发展新理论和发现新材料提供了巨大的空间。尽管ti具有被保护的无间隙边缘或表面状态，并且理论上应该在体中具有绝缘间隙，但迄今为止发现的大多数3D ti仍然在体中具有相当的导电性。材料的设计和加工已经成为研究和发现新材料的关键。材料物理学家面临的挑战是创造出真正的绝缘材料，以促进对其奇异表面状态的研究。在这个建议中，我们描述了要采用的方法，以获得高质量的材料，为不同的实验提出。我们建议合成一系列材料，其中一些已经被称为拓扑绝缘体和其他新材料，如拓扑晶体绝缘体（tci）和那些具有新兴拓扑行为的材料。该项目将研究大块晶体材料和纳米材料（以纳米片和纳米棒的形式）。将对三维ti和tci中超导性的出现进行研究。在超导拓扑绝缘体中存在一个完整的配对间隙，以及这些材料的无间隙表面状态，使它们非常有趣。这些材料的物理特性将通过详细研究晶体的体特性（包括电阻率和霍尔效应、磁化、热容量）来研究，特别是了解体电子和磁性对其拓扑行为的影响。x射线/电子衍射和电子显微镜技术将用于研究晶体和纳米材料的结构特性。XPS和ARPES对晶体和纳米材料表面的研究将与我们的合作者一起进行。中子散射和介子光谱学技术也将被采用。来自项目合作伙伴的宝贵理论输入将与实验调查的结果结合使用，以告知设计和制造具有TI行为的新材料的决定。广泛的专家网络，包括理论家和实验学家，作为合作者将为成功交付本项目所描述的工作做出贡献。

Topological Insulators (TIs) are a class of quantum materials that exhibit topological surface states. These materials are usually small band gap semiconductors where the bulk of the material is insulating, but they exhibit special surface states that are conducting and topologically protected. The materials are usually made of heavy atoms that give rise to strong spin-orbit coupling and this leads to the formation of surface states that are not destroyed by scattering or impurities. TIs are proving to be ideal materials for study in condensed matter physics, as the physics of these materials is novel and they offer huge scope for developing new theories and for the discovery of new materials. Although the TIs have gapless edge or surface states that are protected and are in theory supposed to have an insulating gap in the bulk, most of the 3D TIs discovered to date are still fairly conducting in the bulk. Materials design and processing have emerged as being key to the investigation and the discovery of new TIs. The challenge for materials physicists is to create TI materials that are true insulators in the bulk, in order to facilitate the study of their exotic surface states.In this proposal, we describe the methodology to be adopted to obtain high quality materials, for the different experiments proposed. We propose to synthesize a range of materials, some of which are already known to be Topological Insulators and other new materials such as the Topological Crystalline Insulators (TCIs) and those with emerging topological behaviour. The project will investigate both bulk crystalline materials and nanomaterials (in the form of nanoplatelets and nanorods). The study of the emergence of superconductivity in the 3D TIs and TCIs will be undertaken. The existence of a full pairing gap in the bulk in the superconducting Topological Insulators, together with the gapless surface states in these materials, makes them extremely interesting.The physics of these materials will be investigated through detailed studies of the bulk properties of the crystals (including resistivity and Hall effect, magnetisation, heat capacity) in particular, to understand the influence that the bulk electronic and magnetic properties have on their topological behaviour. X-ray/electron diffraction and electron microscopy techniques will be used for the investigation of the structural properties of both the crystals and nanomaterials. Investigations of the surfaces of the crystalline and nanomaterials by XPS and ARPES will be carried out with our collaborators. Neutron scattering and muon spectroscopy techniques will also be employed. Valuable theoretical input from the Project Partner will be used in conjunction with the results from the experimental investigations, to inform the decisions for the design and fabrication of new materials exhibiting TI behaviour.A wide network of experts, including both therorists and experimentalists, as collaborators will contribute to successfully deliver the work described this project.