Superfluid onset and compressibility of 4He films adsorbed on carbon nanotubes
Abstract
Third sound measurements of superfluid 4He thin films adsorbed on 10-nm-diameter multiwall carbon nanotubes are used to probe the superfluid onset temperature as a function of the film thickness, and to study the temperature dependence of the film compressibility. The nanotubes provide a highly ordered carbon surface, with layer-by-layer growth of the adsorbed film as shown by oscillation peaks in the third sound velocity at the completion of the third, fourth, and fifth atomic layers, arising from oscillations in the compressibility. In temperature sweeps the third sound velocity at very low temperatures is found to be linear with temperature, but oscillating between positive and negative slope depending on the film thickness. Analysis shows that this can be attributed to a linearly decreasing compressibility of the film with temperature that appears to hold even near zero temperature. The superfluid onset temperature is found to be linear in the film thickness, as predicted by the Kosterlitz-Thouless theory, but the slope is anomalous, a factor of 3 smaller than the predicted universal value.
- Publication:
-
Physical Review B
- Pub Date:
- February 2019
- DOI:
- 10.1103/PhysRevB.99.064503
- arXiv:
- arXiv:1711.00951
- Bibcode:
- 2019PhRvB..99f4503M
- Keywords:
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- Condensed Matter - Other Condensed Matter
- E-Print:
- 6 pages, 4 figures, revised version published in PRB