Observation of a superfluid component within solid helium

摘要

We demonstrate by neutron scattering that a localized superfluid component exists at high pressureswithin solid helium in aerogel. Its existence is deduced from the observation of two sharp phonon-rotonspectra which are clearly distinguishable from modes in bulk superfluid helium. These roton excitationsexhibit different roton gap parameters than the roton observed in the bulk fluid at freezing pressure. One ofthe roton modes disappears after annealing the samples. Comparison with theoretical calculationssuggests that the model that reproduces the observed data best is that of superfluid double layers withinthe solid and at the helium-substrate interface.