Transitions and Complex Order at Ultralow Temperatures

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9409590 Osheroff Technical abstract: Helium three will be used as a model system to study various aspects of the nature of phase transitions and complex order in important classes of physical systems. Work on superfluid helium three A-B phase nucleation will probe how surface roughness increases the nucleation rate, possibly paving the way for the use of this system in quantum tunneling studies. Study of the magnetic order in thr second layer helium three films adsorbed on graphite will be continued. The emphasis of this work is to search for a possible finite temperature phase transition in low magnetic fields for this two dimensional Heisenberg system. Third sound studies will be carried out to search for a second superconducting state of sub-monolayer helium three films adsorbed on superfluid helium four. Finally, new studies of the spatial dependence of noise correlations in spin glasses will be carried out. Non-technical abstract: Helium three will be used as a model system for studying various aspects of the nature of phase transitions and complex order in important classes of physical systems. Studies of the phase transitions between two liquid helium three phases which are neutral analogs to electrical superconductors may help produce a highly effective particle detector, as well shed knowledge on a broad class of phase transitions in general. Thin helium three films which exhibit effective magnetic interactions between the atomic nuclei will allow test theoretical predictions that thin liquid helium three films on appropriate substrates may exhibit still more novel forms of order, possibly related to those seen in the oxide superconductors. ***