An acoustic cavity containing 3He in 98% porous silica aerogel was used to investigate the effects of impurity scattering in a Fermi liquid. The pressure and temperature dependence of the sound attenuation in the normal Fermi liquid was extracted from the cavity response. The attenuation of sound displays behavior very different from the bulk owing to strong elastic scattering of quasi-particles by the silica strands. Using a visco-elastic model of the Fermi liquid, we find a mean free path restricted to ∼340 nm. Information on the sound velocity is inferred from the pressure dependence of the oscillation period of the cavity response. The data can be accounted for by a Biot model of the 3He liquid in the porous aerogel.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Materials Science(all)
- Condensed Matter Physics