Non-Equilibrium Interfaces in Strongly Interacting Fermi Gases

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General audience abstract:Next-generation technologies, ranging from magnetically levitated high-speed trains and near-lossless power transmission, to higher-performance devices for quantum computing and computer memory, will depend on materials that, at the microscopic level, achieve higher performance through strong interactions between electrons in the material. However, the strong interactions and correlations between electrons that give rise to advantageous properties, such as more robust superconductivity, also present new challenges in our understanding of these materials. In particular, when strongly correlated materials are driven out of equilibrium and interfaced with other materials, conventional theories often break down, necessitating more powerful theories to handle strong interactions. In this work, the researchers will measure non-equilibrium and transport properties in a quantum gas of strongly interacting lithium atoms that models the quantum behavior of strongly interacting electrons. The project aims to elucidate the fundamental physics of transport in strongly correlated materials out of equilibrium, where existing theories face the greatest challenges. Undergraduate and graduate students contributing to the research will gain skills in planning, conducting, and communicating about scientific work, in preparation for careers in the scientific and technological workforce.Technical audience abstract:This research program will investigate transport and non-equilibrium dynamics at normal-superfluid interfaces and in strongly interacting Fermi gases. The team will implement a multi-region trap for lithium-6 atoms that will allow the preparation of well-defined non-equilibrium initial states. The researchers will employ controllable barrier potentials between the regions to initiate evolution towards equilibrium. Initializing separate normal and superfluid regions will enable the team to characterize transport at the normal-superfluid interface and to observe the dynamics of the interface. These measurements will provide benchmarks to test theories of transport at normal-superfluid and normal-superconductor interfaces for strongly interacting systems. Preparing a sample region in contact with two highly polarized reservoir regions will enable the researchers to measure local spin-transport properties across the superfluid transition. Such measurements will illuminate the relationship between superfluidity and spin transport, the role of pairing correlations in the low-temperature normal phase, and the effect of theorized quantum limits on transport. The approach introduced in this work will lay the foundation for a wide range of novel non-equilibrium measurements in quantum many-body systems.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.