Third sound in layered superfluids: Harrow-down on /sup 4/He
In order to minimize the possibility of spin flips due to interactions with and on the walls of a sample cell, spin-polarized hydrogen (Harrow-down) is studied in a /sup 4/He sample cell, i.e., a sample cell which has been coated with a film of superfluid /sup 4/He. At low temperatures it is expected that the most dense Harrow-down sample will first form in the physisorbed state on the /sup 4/He film. In this paper we examine in detail the hydrodynamic consequences of this lyered film configuration. We derive the expression for third sound in the general case that the films are compressible and both films have undergone superfluid transitions. In this case two propagating modes will be seen which will provide an unequivocal demonstration of a superfluid transtion in the Harrow-down film. We specialized to various limiting cases: incompressible films, saturated and unsaturated films, and the normal fluid Harrow-down blanket. In our discussion we stress the point that even if the Harrow-down has not gone superfluid it will still shift the /sup 4/He third-sound speed, that this shift is a direct measure of the Harrow-down film areal density, and that the magnitude of this shift is expected to be well within the precision of present-day third-sound eperimental techniques. Thus third sound is expected to be a primary diagnostic tool in the study of Harrow-down films.
- Research Organization:
- Laboratory for Low Temperature Physics, Department of Physics and Astronomy, University of Massachusetts, Amherst, Massachusetts 01003
- OSTI ID:
- 5096998
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Vol. 25:9
- Country of Publication:
- United States
- Language:
- English
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