Discovery of New Quantum Materials: Topological Metals, Insulators, and Superconductors

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Electronic devices are everywhere in our daily life: in cell phones, entertainment systems, navigation systems, medical aids, and computerized services such as online banking. Device functionality is controlled by the flow of electric current through the electronic components in each device, and this depends on the materials used in the components. For example, transistors widely used in electronics are made of semiconductors, which allow simple control of the electronic states available to the electrons. The properties of electronic states are governed by a complex interplay between the electron's charge, the periodic arrangements of atoms in the material, internal orbital' and spin' motions of the electrons and, particularly important for this proposal, the coupling between these orbital and spin motions. For instance, in insulators, electrons cannot flow in the interior of a sample because there are no available electronic states. If there is strong spin-orbit coupling, however, there can be available electronic states on the surface of the sample. This recently-discovered class of materials is called topological insulators', because the surface states are a manifestation of quantum physics related to the topology of the electron's quantum-mechanical wave function. Contextually, the term topological' implies robustness against possible impurities in solids at finite temperatures finite electrical conductivity could occur on the surface of topological insulators even at room temperature in impure samples making such materials attractive for a future generation of electronic components. Analogous robust quantum states may occur in metals and superconductors if they are endowed with similar topological protection arising from spin-orbit interactions, to produce so-called topological metals and topological superconductors. My research group does theoretical research on these and other many-body electron systems. We have spent many years inventing and developing techniques that have allowed us to understand the fundamental principles and basic ingredients that operate in topological insulators, metals, and superconductors, and in diverse magnetic materials. We have recently shown that our methods have developed to the point where we can begin to predict new topological materials, and the goal of the present proposal is to apply our methods to discover and foresee new quantum materials that can be tailor-made using modern materials-fabrication methods, such as thin-film and artificial super-lattice growth, to optimize desired functionalities. New quantum hetero-structures and novel interfaces between superconductors and topological materials will also be investigated. This research will involve and help to train the next generation of theoretical materials scientists by exposing them to a broad range of materials ideas and techniques.**