Collective Phenomena in Quantum Fluids

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This project addresses the properties of superfluid He-3 and spin- polarized He-3/He-4 mixtures. He-3 serves as model complex superfluid. Experiments on this system relate to other highly correlated systems, including high-Tc superconductors. The collective modes in the superfluids will be investigated by acoustical methods, including second-sound. Additional experiments will use nuclear magnetic resonance as a characterization probe. The experiments on dilute spin polarized He-3/He-4 mixtures will focus on relaxation process in the fluids which arise via domain wall or soliton motion in the fluids. A goal of the research is to determine the relative importance of direct radiation of radiofrequency, as compared with radiation of spin waves, as a domain wall moves in a magnetic field. %%% This project investigates the fundamental properties of fluids at very low temperatures. These "superfluids" exhibit behavior related to high-temperature superconductors, whose properties remain unexplained. The superfluids also provide model system for studying fundamental thermodynamics of fluid mixtures. Again, the results are relevant to systems at higher temperatures and in practical conditions. Finally, the author has a facility that provides a way to apply a very large magnetic field to the samples and hence carry out unique experiments to study magnetic domain wall motion, and other dynamical behavior exhibited by magnetic materials.