Search for Novel Electronic State in Strongly Correlated Kondo Insulators

在固体中，许多电子相互作用，导致有趣的现象。例如，在一些金属中，它们相互作用使金属成为良好的绝缘体。电子之间的耦合可能具有拓扑特性，使材料的表面导电，同时保持内部体绝缘。对近藤绝缘体（一种基于稀土元素的固体材料）进行的一系列实验揭示了这种惊人的特性。这项研究带来了丰富的新物理学，并为未来电子产品的材料开发带来了希望。该研究进一步加深了对稀土六硼化物的基础认识，并为未来的电子和磁性材料打开了新的大门。高导电性的表面状态在拓扑上不受杂质的影响。因此，基于拓扑相的二维器件有望成为制造下一代纳米场效应晶体管的优越电子纳米材料，具有更快的运行速度、更低的功耗和更高的集成密度，具有超越传统硅基场效应晶体管性能的潜力。本提案的教育目标是向公众讲授固体中电子相互作用的进展，并培养对该领域的兴奋，意识和兴趣。这一目标可通过以下途径实现：1)让本科生参与研究；2)创造机会，促进妇女和少数民族在科学和工程领域的融合；3)向更广泛的公众传播研究成果。密歇根大学的“周六上午物理”公开讲座，以及密歇根大学的“明日科学”项目向低收入地区的中学生进行公开演示和研讨会，可以接触到更广泛的公众，特别是代表性不足的群体。技术摘要：本研究的目的是探讨强相关近藤绝缘子中量子振荡和朗道能级量子化的物理起源。利用扭矩磁强计、电学和热电效应以及热输运特性的测量技术，首席研究员旨在回答近道绝缘体，特别是六硼化钐SmB6的这3个具体问题：(1)量子振荡信号的维度是什么：二维还是三维？(2)在高温下量子振荡振幅如何变化——它是否符合费米液体理论中的Lifshitz Kosevich公式？(3)电输运性质中是否存在量子振荡？振荡是电子的，还是完全电荷中性的？这些问题的答案提供了近藤绝缘体中量子振荡的大图景。如果外来体电荷中性费米表面确实存在，则研究解决了这种体态的热输运特征。从研究中获得的知识揭示了近藤绝缘体的电子状态。该研究解决了近藤绝缘体是具有无漏体电导的拓扑绝缘体还是具有电荷中性费米表面的电子绝缘体的争论。这两种情况都是凝聚态物理的重大突破。

Non-Technical Abstract: In solids, many electrons interact among themselves leading to interesting phenomena. For example, in some metals they interact turning the metal into a good insulator. The coupling between electrons may have a topological property, making the material's surface conductive while keeping the inner bulk insulating. This amazing property is revealed by a number of experiments on Kondo insulators, a family of solid materials based on rare earth elements. The research leads to rich new physics and brings hope for developing materials for future electronics. The research furthers fundamental knowledge of rare earth hexaborides and opens new doors for future electronic and magnetic materials. The highly conductive surface states are topologically protected against impurities. As a result, 2D devices based on topological phases are expected to be able to serve as superior electronic nanomaterials for making next-generation nanoscale field-effect transistors, which have the potential to exceed the performance of conventional silicon-based field-effect transistors, with faster operation speed, lower power consumption, and higher integration density. The educational objective of this proposal is to teach the general public about advancements in electron interactions in solids and to develop excitement, awareness, and interest in the field. This objective is achieved through several avenues: 1) involving undergraduates in research; 2) creating opportunities to promote the integration of women and minorities in careers in science and engineering; and 3) communicating research to the broader public. The broader public, particularly underrepresented groups are reached by public lectures at University of Michigan's Saturday Morning Physics, and by public demonstrations and workshops to middle school students in low-income areas through the University of Michigan's Science for Tomorrow program.Technical Abstract: The objective of the research is to investigate the physical origin of the quantum oscillations and Landau Level quantizations in strongly correlated Kondo insulators. Using measurement techniques of torque magnetometry, electrical and thermoelectric effects, and thermal transport properties, the principal investigator aims to answer these 3 specific questions for Kondo insulators, especially for samarium hexaboride SmB6: (1) What is the dimensionality of the quantum oscillation signals: 2-dimensional or 3-dimensional? (2) How does the quantum oscillation amplitude change at elevated temperatures - does it follow the Lifshitz Kosevich formula from Fermi liquid theory or not? (3) Does quantum oscillation exist in electrical transport properties? Is the oscillation electronic, or completely charge-neutral? Answers to these questions provide the big picture of quantum oscillations in Kondo insulators. If exotic bulk charge-neutral Fermi surface indeed exists, the research resolves the thermal transport signatures of this bulk state. The knowledge obtained from the research sheds light on the electronic state of Kondo insulators. The research resolves the debate on whether Kondo insulators can be topological insulators with no leaky bulk conductance or an electronic insulator with charge-neutral Fermi surfaces. Either scenario is a significant breakthrough in condensed matter physics.