Physics of Non-Fermi Liquid Metals

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NONTECHNICAL SUMMARYThis award supports theoretical research and education in the many-body physics of strongly correlated quantum materials. The textbook description of electrons in solids assumes essentially free electrons, moving throughout the solid independently of what all other electrons are doing. Research in the recent past has shown that this description fails in a wide variety of materials, in which electrons in the solid are strongly correlated with each other. In these quantum materials, strong correlations can produce unusual states of matter, and lead to phase transitions between them. These are the quantum analogues of familiar phase transitions such as ice melting into water, or water boiling into vapor. The PI will develop theoretical methods to study the collective behavior of electrons near such phase transitions to understand how novel types of superconductivity can be generated, and to explore how these states evolve under the influence of external electromagnetic fields.Through the project, the PI will bring about understanding about quantum materials in general, which is a central element of quantum science and technology that has recently emerged as a top national priority. The PI intends to collaborate with leading experimental groups worldwide in this area, thereby creating educational opportunities for graduate and undergraduate students involved in the PI's research program. The advanced theoretical training will help students prepare for future careers in academia or industry.TECHNICAL SUMMARYThis award supports theoretical research and education in the physics of strongly correlated quantum materials. Strong correlations can yield novel phases and unusual excitations. In metallic systems, an outstanding challenge is to understand how the correlations generate physics beyond the Fermi-liquid theory. The proposed research will address this open problem, primarily by using systems with both itinerant electrons and localized moments as a prototype setting. The research will develop and apply controlled theoretical methods to study well-defined microscopic and field-theory models. The research aims to gain new insights that are broadly relevant to the physics of strongly correlated electrons. The PI will pursue four specific research directions: First, the PI will analyze heavy-fermion quantum criticality, with a focus on Kondo lattice systems that contain entwined degrees of freedom. Second, the PI plans to initiate theoretical studies on the novel phases that emerge near quantum critical points, including pairing state of multiorbital superconductivity that is driven by quantum criticality. Third, the PI will explore non-Fermi-liquid physics in heavy-fermion systems potentially hosting Kondo-driven Weyl nodes, thereby elucidating quantum criticality in a new setting. Fourth, the PI will investigate real-time dynamics under driven conditions as a means of probing quantum criticality. Through concrete model studies, this research direction aims to shed light on the coherence and dynamics of strongly coupled quantum systems out of equilibrium.Through the project, the PI will bring about understanding about quantum materials in general, which is a central element of quantum science and technology that has recently emerged as a top national priority. The PI intends to collaborate with leading experimental groups worldwide in this area, thereby creating educational opportunities for graduate and undergraduate students involved in the PI's research program. The advanced theoretical training will help students prepare for future careers in academia or industry.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.