Study of Disorder and the Emergence of a Robust Insulating Behaviour in Topological Kondo Insulator, Samarium Hexaboride

非技术摘要：自然界提供了一种迷人的绝缘材料，具有许多独特的性能，主要是因为它是唯一一种电绝缘体，其性能不会随着杂质或无序的增加而变化很大。对这种被称为六硼化钐的材料的研究不仅因为它的独特性质，而且因为它处于两个科学领域的交叉点--相关的电子系统和拓扑材料。了解这种材料为何具有坚固的绝缘性能是该项目的主要目标。实现这一认识将导致新类型的输运现象，例如通过位错的独特的一维传导，这是不可能的，并且在其他拓扑材料中很难观察到。在这项工作中将开发新的运输方法来探索这种独特的材料，这种材料可以被其他研究许多其他材料的小组广泛使用。此外，这种奇怪的绝缘体，六硼化钐，也是研究拓扑保护的表面电子的出现性质的理想材料。这一点很重要，因为这可以为测试新的和创新的自旋电子和超导-拓扑绝缘体混合设备铺平道路。该项目的教育部分为研究生和本科生提供了极好的培训。首席调查员将参加旨在激发K-12学生对STEM领域的兴趣的外展活动。一本面向所有物理研究生的独特、全面的物理学习手册正在开发中，以帮助学生过渡到研究生研究。技术摘要：最近通过倒置电阻测量发现的绝缘行为对无序的健壮性，使六硼化锶成为最独特的拓扑材料之一。本项目使用倒置电阻、霍尔和科比诺测量方法研究了六硼化锶及其稀合金中的体相和表面电导。为了研究表面传导，采用了另一种输运分析来消除次表面裂纹对输运的贡献。主要目标之一是了解差距的形成和散装运输健壮性的根本原因。为了量化这种材料中无序的影响，研究小组正在对掺La、Fe、La、Ga和Eu的样品进行输运实验，掺杂范围从0.1%到5%。除了点缺陷，这个项目还着眼于扩展的缺陷，包括一维位错，它可以在拓扑绝缘体中形成导电通道。如果成功，单一一维位错输运的实验实现将允许研究一种新的拓扑保护传导模式。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical Abstract:Nature has provided a fascinating insulating material with many unique properties, mainly that it is the only electrical insulator whose properties do not vary much with increasing impurities or disorder. Research on this material, called samarium hexaboride, is important not only because of its unique properties but that it is at the intersection of two scientific fields ‐ correlated electron systems and topological materials. Understanding why this material has robust insulating behavior is the main goal of the project. Achieving this understanding will lead to new kinds of transport phenomena, such as unique one‐dimensional conduction through dislocations that should not be possible and which are difficult to observe in other topological materials. Novel transport methods will be developed in this work to explore this unique material that can be broadly used by other groups studying many other materials. Furthermore, this strange insulator, samarium hexaboride, is also an ideal material for studying the emergent properties of topologically protected surface electrons. This is important because this can pave the way for testing new and innovative spintronic and superconductor‐topological insulator hybrid devices. The educational component of this project provides excellent training for graduate and undergraduate students. The principal investigator will participate in outreach activities that are designed to excite K‐12 students about STEM fields. A unique, comprehensive physics study manual intended for all physics graduate students is being developed to help students to transition into graduate research.Technical Abstract:The robustness of insulating behavior against disorder, which was recently discovered using inverted resistance measurements, makes samarium hexaboride one of the most unique topological materials to study. This project investigates bulk and surface conduction in samarium hexaboride and its dilute alloys using inverted resistance, Hall, and Corbino measurements. To study surface conduction, an alternative transport analysis is employed to eliminate contributions to transport from subsurface cracks. One of the main objectives is to understand the gap formation and the underlying reasons for the robustness of bulk transport. To quantify the effects of disorder in this material, the research team is performing transport experiments on La‐, Fe‐, La‐, Ga‐, and Eu‐doped samples within a dilute doping range from 0.1 to 5%. In addition to point defects, this project looks at extended defects, including one‐dimensional dislocations, which can form conducting channels in topological insulators. If successful, the experimental realization of transport through a single one‐dimensional dislocation would allow the investigation of a new kind of topologically protected conduction mode.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.