Quasiparticle Scattering and Tunneling Spectroscopic Studies on Kondo Lattices, Topological Insulators and Superconductors

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****NON-TECHNICAL ABSTRACT****Understanding how novel electronic states emerge has become a central research topic in condensed matter physics. Identifying the organizing principles for such electronic matter will facilitate discovering materials with novel and useful functionalities. The goal of this project is to investigate this theme in two separate venues: Kondo lattices and topological materials. An entanglement of localized states with itinerant electrons in a so-called Kondo lattice leads to a novel electronic state with greatly enhanced mass at low temperature. How exactly this process occurs and its relationship to a further transition into an ordered state will be studied in detail. For this purpose, measurement techniques to probe how electron waves interfere in such a system will be employed. Novel electronic states, called topological, that cannot be continuously transformed to ordinary states can exist in a certain class of materials and they are known to exhibit exotic properties, such as conducting electricity on their boundaries without dissipation while behaving as insulators for transport through the bulk. In this project, the nature of superconductivity induced in these topological states and the elusive Majorana particles that could potentially help in building a quantum computer in the future, will be probed using similar measurement techniques. Graduate and undergraduate students will take parts in this project by carrying out experiments and data analysis and attending workshops/conferences to disseminate the results.****TECHNICAL ABSTRACT****Recent years have witnessed resurging interest in understanding the organizing principles for novel quantum matter. This project aims at unraveling the underlying mechanism for emergent phenomena in Kondo lattices and topological materials. The hidden order phase in URu2Si2 has long defied an unambiguous determination of its order parameter. Towards resolving this problem, the detailed hybridization process between localized states and itinerant bands and its relationship to the hidden order transition will be investigated using spectroscopic techniques such as quasiparticle scattering and tunneling. Other closely related Kondo lattice systems will also be studied. Novel topological electronic states emerge due to a combined effect of unconventional band structure and Fermi surface topology. Understanding their underlying physics is a frontier research topic. In this project, the nature of proximity-induced superconductivity in topological materials and Majorana fermions predicted to exist in such systems will be probed using tunneling spectroscopy and other phase-sensitive measurements. Graduate and undergraduate students will take parts in this project by carrying out experiments and data analysis and attending workshops/conferences to disseminate the results.