Temperature and drive power dependence of the phase of third sound modes in {sup 3}He - {sup 4}He mixture films

Journal Article · Sat Apr 01 04:00:00 EST 1995 · Bulletin of the American Physical Society

OSTI ID:375051

Sheldon, P A; Hallock, R B ^[1]

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1. Univ. of Massachusetts, Amherst, MA (United States)

The authors report measurements of the frequency, damping (1/Q), and phase between the sinusoidal drive voltage and film thickness fluctuation of third sound modes driven in helium mixture films on a Nuclepore resonator. The properties of the third sound resonance modes are deduced from fits to amplitude versus frequency for mixture films at fixed {sup 4}He, n{sub 4} = 0.39{Angstrom}{sup {minus}2}, as a function of temperature, 40 mK {le} T {le} 500 mK and {sup 3}He coverage, 0.01 {le} n{sub 3} {le} 0.06{Angstrom}{sup {minus}2}. At low temperatures and low drive powers the phase appears to be about 180 degrees. This indicates that when the temperature of the driver is a maximum, the film thickness above it is a minimum. At 200 mK there is an abrupt change to a phase of zero, and the phase remains at zero for all drive powers for T > 200mK. Bergman predicts a 180 degree phase difference between the temperature and film thickness fluctuation in a third sound wave, and this was seen in pure {sup 4}He films. The change in phase observed here may be related to the pulse inversion seen in earlier third sound work at higher coverages of {sup 3}He.

• OSTI ID: 375051
• Report Number(s): CONF-9304297--
• Journal Information: Bulletin of the American Physical Society, Journal Name: Bulletin of the American Physical Society Journal Issue: 2 Vol. 40; ISSN 0003-0503; ISSN BAPSA6
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
FILMS
HELIUM 3
HELIUM 4
MIXTURES
PHASE STUDIES
SUPERFLUIDITY
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0000-0013 K
THIRD SOUND