Inelastic neutron scattering measurements of the roton in superfluid helium confined in two different porosity aerogels are presented. The temperature dependence of the roton energy exhibits an anomalous crossover behavior at Tc = 1.9 K. Below Tc the roton energy is found to be weakly temperature dependent while above Tc it is very strongly temperature dependent. The roton lifetime for the confined liquid also displays a weak crossover behavior. A simple qualitative model for this behavior in terms of a confined length scale is discussed.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering