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

摘要：大自然提供了一种迷人的绝缘材料，它具有许多独特的性能，主要是它是唯一一种随着杂质或无序度的增加而性能变化不大的电绝缘体。对这种被称为六硼化钐的材料的研究非常重要，不仅因为它具有独特的性质，而且因为它处于两个科学领域的交叉点——相关电子系统和拓扑材料。了解为什么这种材料具有强大的绝缘性能是该项目的主要目标。实现这种理解将导致新的输运现象，例如通过位错产生的独特的一维传导，这在其他拓扑材料中是不可能的，也很难观察到。在这项工作中，新的运输方法将被开发出来，以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，也是研究拓扑保护表面电子涌现特性的理想材料。这很重要，因为这可以为测试新的和创新的自旋电子和超导体-拓扑绝缘体混合器件铺平道路。这个项目的教育部分为研究生和本科生提供了良好的培训。首席研究员将参与旨在激发K - 12学生对STEM领域兴趣的外展活动。一个独特的，全面的物理研究手册旨在为所有物理研究生正在开发，以帮助学生过渡到研究生研究。技术摘要：最近通过反向电阻测量发现，六硼化钐对无序的绝缘行为具有鲁棒性，这使得六硼化钐成为最独特的拓扑材料之一。本项目研究六硼化钐及其稀合金的体积和表面导电性，采用倒电阻、霍尔和科尔比诺测量。为了研究表面传导，采用另一种输运分析来消除地下裂缝对输运的贡献。其中一个主要目标是了解间隙的形成和散装运输稳健性的潜在原因。为了量化这种材料中无序的影响，研究小组正在对La‐，Fe‐，La‐，Ga‐和Eu‐掺杂样品在0.1%至5%的稀释掺杂范围内进行输运实验。除了点缺陷外，该项目还研究了扩展缺陷，包括可以在拓扑绝缘体中形成导电通道的一维位错。如果成功，通过单一一维位错传输的实验实现将允许研究一种新的拓扑保护传导模式。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.