Effects of He-3 impurities on the mass decoupling of He-4 films

Article

关键词: HEAT-CAPACITY;    FRICTION;   

DOI  :  10.1103/PhysRevB.102.104104

来源: SCIE

【 摘 要 】

We performed quartz crystal microbalance experiments using a 5-MHz AT-cut crystal for superfluid He-4 films on exfoliated graphite (Grafoil) containing up to 0.40 atom/nm(2) He-3. We found that the mass decoupling of He-4 solid layers from the oscillating substrate is considerably sensitive, even with small amounts of He-3. For a He-4 film of 29.3 atoms/nm(2), we observed a small drop in resonant frequency at a T-3 of similar to 0.4 K for a low oscillation amplitude, which is attributed to the sticking of He-3 atoms at the He-4 solid layer. For higher amplitudes, the He-4 solid layer shows a reentrant mass decoupling at T-R close to T-3. This decoupling can be explained by the suppression of the superfluid counterflow owing to the adsorption of the He-3 atoms on edge dislocations. As the He-4 areal density increases, T-R shifts to a lower temperature and disappears around the He-4 film of 39.0 atoms/nm(2).

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