Novel Thermal Transport Phenomena in Quantum Materials

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Non-technical Abstract: In solids, electrons carry not only electrical charges but also heat and energy. This dual nature of electrons turns out to be a powerful tool to understand quantum materials. Moving the electrons with heat creates electrical voltages or reveals thermal conductions in the solids. These mobile electrons may further change the moving directions under a magnetic field, leading to transverse electrical voltages and transverse thermal conductions. These novel thermal transport properties are essential steps to detect and probe the ground state of strongly correlated quantum materials. The research brings the potential to open the door to study the interplay between strong-correlation effects and topology in the search for new quantum phases, novel topological phases, and new multi-functionalities for future electronics. The project also provides opportunities to train undergraduate and graduate students in the science and technology of this field anticipated to grow in the coming years. By involving undergraduates in research, integrating female and minority students in the projects, and communicating research to the broader public, the team brings the general public the advancements in strongly correlated materials and to develop excitement, awareness, and interest in the field of quantum science and condensed matter physics. Technical Abstract: The research project aims to investigate strongly correlated materials using novel thermal transport properties. Bridging the research fields of strongly correlated materials and topological quantum materials, the research team will use thermoelectric effect and thermal Hall effect to reveal the physical origin of recently observed novel phenomena of strongly correlated materials: (1) quantum oscillations in electrical resistivity of Kondo insulators; (2) large thermal Hall effects in Mott insulating state of the undoped parent compound of high-temperature superconductors, and (3) topological superconducting state in Fe-based superconductors. These directions are new exciting developments in long-standing puzzles in condensed matter physics. They share the same debate about the role of the charge-neutral quasiparticles in the strongly interacted states: what carries these interesting phenomena: magnon, phonon, and Bogoliubov quasiparticles. The research tasks will answer these questions: (1) What is the nature of the quantum oscillations in insulators? (2) What leads to the metal-like thermal transport in Kondo insulators? (3) Why are Hall signals of the heat flow in undoped cuprates? (4) How to couple to quantum anomalous vortices in Fe-based topological superconductors? The answers to these questions shed light on the ground state of the strongly interacted quantum systems. The research also leads to effective ways to probe charge-neutral quasiparticles in strongly correlated quantum materials and reveal the crucial characteristics in these material systems.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.