This research focuses on the response of superfluid 3He B to the presence of structures much smaller than the superfluid coherence length, x. These results can serve as a paradigm for understanding how other unconventional BCS states, such as the oxide superconductors, will respond to the presence of impurities. In this work, the bending stiffness of the order parameter will be measured for the first time by growing aerogel within an array of parallel plates. Here the magnetic field competes with surface effects to orient the order parameter. In a separate collaboration with Frank Gasparini of the University of Buffalo, the superfluid 3He density will be studied in channels accurately etched in silicon substrates. This will allow the first accurate measurements of the superfluid gap suppression in well-defined confining geometries. Another experiment will study the mobility of domain walls in U2D2 nuclear spin ordered solid 3He, to see if this system might be a candidate for studying macroscopic quantum tunneling. Graduate students involved in these projects will receive training in ultra-low temperature refrigeration techniques, NMR spectroscopy, and the design of sophisticated apparatus. This training has allowed previous students to go on to successful careers in academia, national laboratories, and industry. %%% This work will study how the scattering of superfluid 3He by strands just 5 nm in diameter in silica aerogels alter the properties of the superfluid. This is a macroscopic quantum state, directly analogous to that in superconductors, particularly the high temperature oxide superconductors. In both cases impurity scattering can destroy the ordered state. By studying how the superfluid is oriented in an aerogel sample grown in the gaps between parallel plates using NMR techniques, it will be possible to measure how this scattering affects the stiffness of the ordered state to bending for the first time. In a separate collaborative study with Frank Gasparini, University of Buffalo, superfluid 3He will be studied in well-defined narrow channels etched in silicon substrates. This will allow an accurate first measurement of the suppression of superfluidity by well defined, highly confining geometries. These results should be useful in understanding how a broad class of superfluids and superconductors will be affected by impurity scattering and confinement, from the high Tc superconductors to the dense matter in neutron stars. Students in this program learn techniques and materials physics that allow them to pursue careers in academe government, and industrial settings.
