Collective modes in superfluid helium when there is a relative velocity between the normal and superfluid components

• Published in: Физика низких температур
• Date: 2008
• Main Authors: Adamenko, I.N., Nemchenko, K.E., Slipko, V.A., Wyatt, A.F.G.
• Format: Article
• Language: English
• Published: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2008
• Subjects: Жидкий гелий
• Online Access: https://nasplib.isofts.kiev.ua/handle/123456789/116916
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: Collective modes in superfluid helium when there is
 a relative velocity between the normal and superfluid
 components / I.N. Adamenko, K.E. Nemchenko, V.A. Slipko, A.F.G. Wyatt // Физика низких температур. — 2008. — Т. 34, № 4-5. — С. 357–366. — Бібліогр.: 17 назв. — англ.

Collective modes are studied in superfluid helium when the normal and superfluid components have a
 relative velocity w. In this paper the general dispersion relation for first and second sound modes is obtained
 for arbitrary values of w, and we have found the relationship between the amplitudes of the oscillating variables
 for first sound. It is shown in a first sound wave, that both temperature and pressure can oscillate, and
 moreover, the normal fluid velocity can exceed the superfluid velocity in the wave. In the general case of
 first sound, the normal fluid not only has a velocity component parallel to the wave vector, but also a transverse
 velocity component. It is shown that when there is only a phonon system in the helium, the amplitude
 of the temperature oscillation in a first sound wave in an anisotropic phonon system, can exceed that in a second
 sound wave in an isotropic phonon system, for similar values of the normal fluid density.