Transport Properties near the Superfluid Transition in Helium
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概要
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Description are given primarily on recent experimental results and related topics of acoustic attenuation and dispersion, and of thermal transport properties near the superfluid transition in pure ^4He and ^3He-^4He mixtures (≲40% ^3He). Attenuation and dispersion of sound above the lambda point T_λ can well be understood fundamentally from the dynamic scaling hypothesis with the mode coupling theory. Attenuation and dispersion at T_λ as a function of frequency is expressed with the exponent which is slightly dependent on frequency and on ^3He concentration. The situation below T_λ would still have problems since at higher frequencies the simple splitting of observed attenuation and dispersioninto that due to order-parameter fluctuation and that due to order-parameter relaxation proposed by Pokrovskii and Khalatnikov does not work. The possibility that the recent theory of Ferrell and Bhattacharjee offers explanations for the results above and below T_λ is discussed. Thermal conductivity in ^4He and mixtures, and thermo-diffusion ratio in mixtures are measured near the superfluid transition points. Thermal conductivity in the absence of a concentration gradient and its corresponding thermal diffusivity are then calculated. The critical exponent of this thermal diffusivity is approximately 1/3, irrespective of ^3He concentration. The thermo-diffusion ratio has very weak divergence, if any, when T_λ is approached. Two damping modes in mixtures in non-stationary condition are then calculated. Only the mode corresponding to the Brillouin linewidth does diverge with critical exponent approximately equal to 1/3, irrespective of ^3He concentration.
- 社団法人応用物理学会の論文
- 1980-12-05
著者
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IKUSHIMA Akira
The Institute for Solid State Physics, The University of Tokyo
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Ikushima Akira
The Institute For Solid State Physics The University Of Tokyo
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