Superfluidity in helium films studied with a thin-film oscillator

• Published in: Physica B + C Vol. 124; no. 1; pp. 1 - 21
• Main Authors: Bannink, G., Brocken, M.G.M., Van Andel, I., Van Beelen, H.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.01.1984; North-Holland
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dielectric thin films; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Exact sciences and technology; Physics; Thickness; Helmholtz resonator; Experimental study; Superfluidity; Third sound; Thin film; Sound velocity
• ISSN: 0378-4363
• DOI: 10.1016/0378-4363(84)90026-3

In this article on measurements of superfluidity in 4He films a detailed report on the construction of the isothermal thin-film Helmholtz oscillator is presented. The design and the performance of the film-thickness transducers are discussed. Measurements of Helmholtz oscillations and low-frequency third-sound phenomena, both excited in the oscillator, are analysed in terms of a phenomenological two-fluid model. When proper account is taken of the flow of mass and energy between the film and its environment, a consistent description of these independent phenomena is obtained. Combining the data derived for the areal superfluid density in the film with the onset data from the thermo-mechanical effect measurements yields strong numerical support for the applicability of the Kosterlitz-Thouless prediction for two-dimensional ordering in very thin films. Finally, also a phase diagram for the mobility of thin films as deduced from the existing experimental evidence is given.