Excitations and thermodynamics for liquid-helium films

W. F. Saam, Milton Walter Cole

Research output: Contribution to journalArticle

201 Citations (Scopus)

Abstract

We derive a hydrodynamic theory of the long-wavelength excitations of helium films adsorbed in cylindrical pores and on planar substrates. In the case of cylindrical geometry, the spectrum exhibits an instability for a particular value of the ratio of the film surface radius to the pore radius. This instability condition is shown to coincide with a thermodynamic instability condition determined by the relative magnitude of the surface energy and the energy of interaction with the substrate. Calculated adsorption isotherms show a corresponding hysteresis in good agreement with measured values. We suggest the possibility that the soft modes present for films thinner than the unstable limit mediate an attractive interaction between quasiparticles of a He3 film adsorbed on the He4, leading to a new kind of He3 superfluid. Similar calculations are presented for the spectrum of He4 on a planar substrate. In this case, as well as in the cylindrical case, surface excitations (ripplons) dominate the thermodynamic properties at low temperature (T0.1 K). In this regime the properties are a simple function of the dimensionality of the surface. At higher T, short-wavelength modes contribute, and the results depend in a complicated fashion on the finite dimensions of the system. We discuss the available data, where possible, and suggest further experiments.

Original languageEnglish (US)
Pages (from-to)1086-1105
Number of pages20
JournalPhysical Review B
Volume11
Issue number3
DOIs
StatePublished - Jan 1 1975

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helium film
liquid helium
thermodynamics
excitation
porosity
radii
wavelengths
surface energy
isotherms
thermodynamic properties
hysteresis
hydrodynamics
interactions
adsorption
thin films
geometry
energy

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

Cite this

Saam, W. F. ; Cole, Milton Walter. / Excitations and thermodynamics for liquid-helium films. In: Physical Review B. 1975 ; Vol. 11, No. 3. pp. 1086-1105.
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Excitations and thermodynamics for liquid-helium films. / Saam, W. F.; Cole, Milton Walter.

In: Physical Review B, Vol. 11, No. 3, 01.01.1975, p. 1086-1105.

Research output: Contribution to journalArticle

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AB - We derive a hydrodynamic theory of the long-wavelength excitations of helium films adsorbed in cylindrical pores and on planar substrates. In the case of cylindrical geometry, the spectrum exhibits an instability for a particular value of the ratio of the film surface radius to the pore radius. This instability condition is shown to coincide with a thermodynamic instability condition determined by the relative magnitude of the surface energy and the energy of interaction with the substrate. Calculated adsorption isotherms show a corresponding hysteresis in good agreement with measured values. We suggest the possibility that the soft modes present for films thinner than the unstable limit mediate an attractive interaction between quasiparticles of a He3 film adsorbed on the He4, leading to a new kind of He3 superfluid. Similar calculations are presented for the spectrum of He4 on a planar substrate. In this case, as well as in the cylindrical case, surface excitations (ripplons) dominate the thermodynamic properties at low temperature (T0.1 K). In this regime the properties are a simple function of the dimensionality of the surface. At higher T, short-wavelength modes contribute, and the results depend in a complicated fashion on the finite dimensions of the system. We discuss the available data, where possible, and suggest further experiments.

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