Effect of adsorption of [sup 3]He and [sup 4]He on the low-temperature ultrasonic properties of porous Vycor

Journal Article · Wed Sep 01 04:00:00 EDT 1993 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.48.6293· OSTI ID:6213568

Mulders, N ^[1]; Molz, E; Beamish, J R ^[2]

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1. Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States)
2. Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2J1 (Canada)

Ultrasonic measurements show that porous Vycor glass has a two-level system (TLS) density of states and a one-phonon--TLS coupling strength very similar to [ital a]-SiO[sub 2]. In addition, because of the sharply reduced sound speed in Vycor, the effect of the first-order Raman process is clearly observable. Introduction of [sup 3]He and [sup 4]He in the pore space causes an increase of the TLS relaxation rates. This results in a shift to lower temperature of the relaxation contribution to the changes in the sound speed and the ultrasonic attenuation. The effect is strongly coverage dependent. This can be most clearly observed in the ultrasonic attenuation around 100 mK. With [sup 3]He we observe a gradual increase with coverage [ital n], which saturates for [ital n][gt]22 [mu]mol/m[sup 2]. With [sup 4]He we see similar behavior for low [ital n], but the attenuation reaches a maximum for [ital n] close to [ital n][sub [ital c]], the critical coverage for the onset of superfluidity. For higher coverage it drops back to approximately half its maximum value. With completely filled pores the contribution to the sound speed shows a clear scaling with [ital T][sup 4]/[omega], in contrast to the [ital T][sup 3]/[omega] or [ital T][sup 7]/[omega] behavior expected for the direct and Raman relaxation processes.

• OSTI ID: 6213568
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 48:9; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

665430* -- Other Topics in Quantum Fluids & Solids-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ADSORPTION
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
HELIUM 3
HELIUM 4
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
MATERIALS
NUCLEI
POROUS MATERIALS
RAMAN EFFECT
RELAXATION
SORPTION
SOUND WAVES
STABLE ISOTOPES
TEMPERATURE RANGE
TEMPERATURE RANGE 0000-0013 K
ULTRASONIC WAVES
VYCOR