ISSN:
1573-7357
Keywords:
67 40 Hf
;
67.40 Vs
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract The velocity threshold for phase slips, vc, has been measured in ultra-pure4He and ultra-dilute3He-4He mixtures, down to a temperature of 15 mK. These experiments have revealed a crossover from a temperature-dependent régime above ∼ 150 mK to a plateau of v c below in ultra-pure4He. Concentrations of3He impurities as low as a few parts in 10−9 greatly affect the plateau régime, causing v c to decrease markedly at low temperature. These observations are interpreted in the framework of the nucleation, either thermally activated or by quantum tunnelling, of vortices in the approximate shape of half-rings. These vortices form on wall asperities at local velocities us estimated to be ∼ 22 m/s in these experiments. The half-ring model is shown to yield a critical velocity of the same magnitude but leaves many basic questions unanswered.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00692047
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