Elementary excitations and sound speed in liquid 4He at negative pressures

We present neutron scattering measurements of the phonon-roton excitations of superfluid 4He at negative pressures in the porous medium MCM-41. The phonon and maxon energies decrease systematically below bulk values as the density is decreased below the bulk value due to stretching of the liquid. Th...

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Bibliographic Details
Published in:Journal of low temperature physics 2005, Vol.138 (1-2), p.31-36
Main Authors: ALBERGAMO, Francesco, BOSSY, Jacques, GLYDE, Henry R
Format: Article
Language:English
Subjects:
Boson degeneracy and superfluidity of 4he
Condensed matter: structure, mechanical and thermal properties
Exact sciences and technology
Physics
Quantum fluids and solids
liquid and solid helium
Quantum statistical theory
ground state, elementary excitations
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Summary:We present neutron scattering measurements of the phonon-roton excitations of superfluid 4He at negative pressures in the porous medium MCM-41. The phonon and maxon energies decrease systematically below bulk values as the density is decreased below the bulk value due to stretching of the liquid. The negative internal pressures are estimated by comparison of the observed maxon energies with extrapolation of positive pressure values and from the sound speed. The maximum negative pressure realized, about -5.5 bar, is consistent with surface tension arguments and the MCM-41 pore diameter of 47 A. Slight broadening of the intrinsic lineshape is observed, suggesting shorter lifetimes of the excitations.
ISSN:0022-2291
1573-7357
DOI:10.1007/s10909-005-1523-9