The Effect of Film Thickness and the Substrate on Superfluid 3He Film Flow
The self-emptying beaker technique was used to study the superfluid properties of thin film liquid 3He. Superfluid film flow was observed only below the bulk transition temperature at 0.93 mK. In a separate experiment the minimum film thickness was determined as a function of 3He level in the beaker. Thus, the flow rate, or critical current density, was determined as a function of temperature and film thickness. Extrapolation allowed a determination of the critical temperature (Tc) and zero temperature critical current density Jc (0) as a function of film thickness. Tc agreed with the predicted superfluid-normal phase boundary at 2d/(T) ç a where d is the film thickness and ξ(T) is the coherence length. Jc (0) was an order of magnitude smaller than expected for dissipation by pair-breaking. When a 4He monolayer was adsorbed on the surface of the beaker, it suppressed the diffuse scattering of 3He quasiparticles at the substrate boundary, as also observed by Freeman et al. There was no measurable suppression of Tc even for films as thin as 100 nm. With or without the 4He monolayer teere was always an abrupt drop in the flow-rate when the film thinned to about 200 nm. This may be associated with the transition between the expected thick film B-like phase and thin film A-like phase.
KeywordsMagnesium Helium Coherence Cerium Lanthanum
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