DMREF: Collaborative Research: Discovering Insulating Topological Insulators

非技术摘要：电子设备的核心是硅，这是一种半导体材料，可以制造出足够高的性能，并适合大规模生产。虽然这样的电路不断改进，但硅无法表现出在天气预报、基因组学和安全加密等方面的完整解决方案所需的量子现象。一种新的材料，即所谓的拓扑绝缘体，有望实现这些现象并使计算发生革命性的变化。理论上，拓扑绝缘体在材料内部是非金属的，但在表面表现得像金属一样。此外，这些金属电子的量子特性可以切换，这是基本的信息处理功能。虽然已知的拓扑绝缘体显示了金属的表面状态，但这些材料还没有被提纯到足以集成到电子器件中。具体地说，它们在室内还没有隔热。该项目将寻求寻找新的拓扑绝缘体，并将其设计成达到绝缘内部所需的纯度水平，并满足电子电路的性能要求。该项目将对电子工业以及熟练掌握这种新型材料的计算和实验技术的培训人员产生影响。技术摘要：该项目的目标是创造出体积足够纯净的拓扑绝缘体材料，以表现出真正的绝缘行为。在含有高Z原子的半导体中发现了拓扑绝缘体，其带隙足够小，以至于与大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。该项目将在含有Ir、Re和Os等重金属的准二元和焦绿石相关结构中探索候选材料类别。材料的固相化学合成将以基于密度泛函理论的模拟为指导。有希望的候选材料将通过适当的方法以单晶的形式合成，包括蒸汽传输、区域细化和助熔剂生长。晶体样品将用角度分辨光电子能谱和传统的电荷传输技术进行研究。原型电阻器件将在这些系统的较小子集上制造。每个测量阶段的结果将反馈给理论和综合工作。

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.