Nonequilibrium Quantum Mechanics of Strongly Correlated Systems

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TECHNICAL SUMMARYThis award supports theoretical research and education to study of nonequilibrium phenomena in strongly correlated quantum systems. The research has three thrusts:1). Quench dynamics in closed quantum systems with applications to cold-atomic gases and toultra-fast pump-probe spectroscopy of solid-state systems. The PI will build on her recent work where a novel renormalization group approach to study the dynamics of strongly correlated systems near critical points was developed. The PI aims to generalize this approach to study: one-dimensional systems where both disorder and interactions are present, quantum quenches in higher spatial dimensions, and a new kind of dynamical phase transition where a closed quantum system in the thermodynamic limit shows non-analytic behavior during its time-evolution. 2). Light-matter coupled systems where the interaction between two-level systems and photons can effectively lead to strongly correlated states of photons. The PI will include both strong driving and dissipation, which appear in experimental realizations of these systems, in the study of these systems. The PI will explore how different kinds of dissipative environments which are non-Markovian in nature affect the physics of the correlated states.3). Transport in nanoscale systems. Nonperturbative methods such as 1/N expansion techniques will be used to study the underscreened Kondo model in which a spin much greater 1 is coupled to current carrying leads. This part of the project has relevance to transport through spin clusters.This award supports active participation of graduate and undergraduate student, and the PI's efforts in K-12 outreach activities that are part of a continuing partnership between the NYU physics department and local schools. NON-TECHNICAL SUMMARYThe award supports theoretical research and education to explore the properties of quantum mechanical systems, such as small assemblies of atoms, that are far from the steady balance of equilibrium. This nonequilbrium state often results when the quantum mechanical system has been subjected to strong forces that act for a short period of time causing the system to change rapidly with time. Important questions arise as to how the system changes in time and how long the system takes to eventually establish a balance with its surroundings. Another way for a quantum system to go out of balance is by subjecting it to a continuous application of an external force. Large and complex systems, despite the steady application of a force, can reach a steady state that is independent of time. This time-independent state can have unusual properties not encountered in systems that are in balance with their surroundings. The PI plans to explore quantum systems in these two kinds of out of balance situations. Out-of-balance systems are challenging topics to study; the PI will develop new theoretical techniques to advance understanding of these ubiquitous systems. Understanding out of balance systems at a fundamental level is important for technological advancement such as for the development of future devices that will be nanometer sized, like a molecule, and will be manipulated by the flow of electric current and by light. On this scale the distinction between material and device becomes blurred.The proposal has a strong educational component as it will involve active participation of graduate and undergraduate students. The results of the projects will be presented at schools, workshops and conferences by the students as well as the PI. In addition, the PI will participate in outreach activities that are part of a continuing partnership between the NYU physics department and local schools.