Porosity dependence of sound propagation in liquid $^4$He filled aerogel
arXiv:cond-mat/0312485 · doi:10.1134/1.1804219
Abstract
Longitudinal sound wave propagation has been studied in an aerogel-liquid $^4$He 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.
4 pages, 3 figures. The paper has been submitted to PRL on 16 June 2003 and has been declined by Editors on 17 December 2003