Physics of Non-Fermi Liquid Metals

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NON-TECHNICAL SUMMARY:This award supports theoretical research and education on the physics of strongly correlated quantum materials. While the textbook description of electrons in solids has been enormously successful in describing conventional metals such as Aluminum and simple semiconductors such as Silicon, its reliance on essentially independent electrons has proven to be inadequate for a broad range of quantum materials. Electrons in such materials cannot be considered to move independent of each other, as they experience strong correlations with each other. Such correlations can produce novel quantum phases and give rise to phase transitions at the absolute zero of temperature. These are quantum analogues of familiar phase transitions such as water freezing into ice. In a class of such quantum phase transitions, electrons act in a highly collective way and a “strange-metal” behavior develops. The PI will apply or develop theoretical methods to study this strange-metal physics near such quantum phase transitions including a type of a phase in which electrons flow without any loss of energy (superconductivity) that may be relevant for quantum information technologies. The fundamental knowledge gained from these studies could, in the long run, help in significant technological advances in the areas of quantum computation, quantum sensing and metrology. The research will create training opportunities for postdocs, graduate students, and undergraduate students who will form the future workforce in quantum science and technology. This award will also support the preparation of a book on "Heavy Fermions and Quantum Phase Transitions" intended for graduate students taking a one-semester course. The PI will disseminate research advances in the area of quantum materials by writing review articles and organizing workshops, which will help in educating and training junior scientists and students in topics at the forefront of condensed matter physics.TECHNICAL SUMMARYThis award supports theoretical research in the physics of strongly correlated quantum systems. The general goal is to understand how strong correlations lead to unusual excitations and novel quantum phases in metallic systems. The PI will apply and develop controlled theoretical methods to study well-defined theoretical models. Four specific research directions will be pursued. First, heavy fermion quantum criticality will be analyzed, with a focus on new regimes characterized by singular charge responses. Second, the PI will initiate theoretical studies on the novel phases that emerge near quantum critical points, with a particular focus on candidate spin-triplet superconductivity. Third, non-Fermi liquid physics in Weyl-Kondo semimetal systems will be explored. Fourth, the PI will investigate out-of-equilibrium physics of quantum critical systems. The research will create training opportunities for postdocs, graduate students, and undergraduate students who will form the future workforce in quantum science and technology. This award will also support the preparation of a book on "Heavy Fermions and Quantum Phase Transitions" intended for graduate students taking a one-semester course. The PI will disseminate research advances in the area of quantum materials by writing review articles and organizing workshops, which will help in educating and training junior scientists and students in topics at the forefront of condensed matter physics.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.