DMREF: Collaborative Research: Discovering Insulating Topological Insulators

非技术摘要：电子设备的核心是硅，一种半导体材料，它可以被制造得足够纯净以获得高性能，并且适合大规模生产。尽管这样的电路在不断改进，但硅却无法表现出在天气预报、基因组学和安全防护等方面的完整解决方案所需的量子现象。一类新材料，即所谓的拓扑绝缘体，有望实现这种现象并彻底改变计算。拓扑绝缘体在理论上是材料内部的非金属，但在表面表现得像金属，而且这些金属电子的量子特性可以转换，这是基本的信息处理功能。虽然已知的拓扑绝缘体展示了金属表面状态，但是这些材料还没有被制成足够纯以并入电子设备中。具体来说，他们还没有在内部绝缘。该项目将寻求找到新的拓扑绝缘体，并将其设计到绝缘内部所需的纯度水平，并满足电子电路的性能要求。该项目将影响电子工业以及培养熟练掌握这类新材料的计算和实验技术的毕业生。技术摘要：该项目的目标是创造拓扑绝缘体材料，这种材料在本体中足够纯净，能够表现出真正的绝缘行为。拓扑绝缘体存在于含高Z原子的半导体中，其带隙足够小，与大Z数相关的自旋-轨道耦合可以反转导带和价带。这些材料还必须具有相关轨道的空间反转对称性。该项目将探索含重金属如Ir，Re，材料合成固态化学技术将指导基于密度泛函理论的模拟。有希望的候选材料将通过适当的方法合成，包括气相传输，区域细化，从助熔剂生长。晶体样品将用角分辨光电子能谱和传统的电荷输运技术进行研究。原型晶体管器件将在这些系统的一个较小的子集上制造。每个测量阶段的结果将反馈到理论和综合工作中.

Non-technical abstract:At the heart of electronic devices lies silicon, a semiconductor material that can be madepure enough for high performance and is amenable to mass production. While suchcircuitry is continually improving, silicon is unable to exhibit quantum phenomenarequired for complete solutions in weather prediction, genomics, and secure encryption.A new class of materials, the so-called topological insulators, holds the promise torealize such phenomena and revolutionize computing. Topological insulators are, intheory, non-metallic in the interior of the material but behave like a metal at the surface.In addition, the quantum character of these metallic electrons can be switched, which isthe basic information processing function. While known topological insulatorsdemonstrate the metallic surface state, these materials have not been made pure enoughfor incorporating into electronic devices. Specifically, they are not yet insulating in theinterior. This project will seek to find new topological insulators and to engineer them tolevels of purity needed for an insulating interior and satisfy the performance demands ofelectronic circuits. The project will impact the electronics industry as well as traingraduates skilled in the computational and experimental techniques of this new class ofmaterials.Technical abstract:The goal of the project is to create topological insulator materials that are pure enough inthe bulk to exhibit true insulating behavior. Topological insulators are found amonghigh-Z atom containing semiconductors with band gaps small enough that the spin-orbitcoupling related to the large Z-number can invert the conduction and valence band.These materials must also possess spatial inversion symmetry for the relevant orbitals.The project will explore candidate materials classes among pseudo-binary andpyrochlore-related structures containing heavy metals such as Ir, Re, and Os. Materialssynthesis by solid state chemistry techniques will be guided by simulations based ondensity functional theory. Promising candidate materials will be synthesized in singlecrystal form by appropriate methods including vapor transport, zone refinement, andgrowth from flux. Crystalline specimens will be studied with angle resolvedphotoemission spectroscopy and conventional charge transport techniques. Prototypetransistor devices will be fabricated on a smaller subset of these systems. The results ateach measurement stage will be fed back to the theory and synthesis efforts.