Porosity dependence of sound propagation in liquid 4He filled aerogel
K. Matsumoto+, Y. Matsuyama+, D. A. Tayurskii+*, K. Tajiri
+Department of Physics, Kanazawa University, Kakuma-machi, 920-1192 Kanazawa, Japan *Physics Department, Kazan State University, 420008 Kazan, Russia Ceramics Research Institute, National Institute of Advanced Industrial Science and Technology, 463-8560 Magoya, Japan
PACS: 67.40.Hf. 67.40.Pm, 67.40.Yv
Abstract
Longitudinal sound wave propagation has been studied in
an aerogel-liquid 4He system for various porosities of aerogel.
The superfluid transition was identified as the absorption peak,
whose magnitude was suppressed by aerogel. The sound velocity was
analyzed within a hydrodynamic theory in both normal and
superfluid phases. The absorption peak due to phonon-roton
interaction around 1 K was not observed even with the most porous
aerogel. The low temperature sound velocity and attenuation show
that direct collisions of phonons with aerogel strands plays an
important role in the acoustic properties.
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