J. Phys. IV France 10 (2000) Pr7-163-Pr7-167
Liquid helium in confinementB. Fak1, O. Plantevin1 and H.R. Glyde2
1 Département de Recherche Fondamentale sur la Matière Condensée, SPSMS/MDN, CEA Grenoble, 38054 Grenoble cedex 9, France
2 Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, U.S.A.
We discuss the effects of confinement and disorder on the elementary excitations of superfluid 4 He in porous media as observed by inelastic neutron scattering. The three-dimensional bulk-like phonon-roton excitations of liquid 4He in aerogel and Vycor are the same as in bulk 4He at low temperatures, with the same temperature dependence. In addition to these excitations, two-dimensional layer modes, which propagate in the first few liquid layers close to the substrate, are observed in both Vycor and denser aerogels near the roton wave vector, with a rotonlike dispersion.
© EDP Sciences 2000