Search for Novel Electronic State in Strongly Correlated Kondo Insulators

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

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.