Helium: Solid-liquid interfaces

The static and dynamic properties of solid-liquid interfaces in helium at low temperature are reviewed. The main emphasis is on the hcp solid 4He-superfluid 4He interface. However, the bcc solid 4He, 3He and 3He-4He mixtures are also considered. Experiments and theoretical work on the dynamics of rough interfaces are first examined. For these interfaces the growth resistance, the Kapitza resistance and the Peltier coefficient are described. Then, static properties such as surface tensions, wetting and contact angles, nucleation and orientation of crystals are considered. The problem of the roughening transition, i.e. the appearance of smooth facets on the interface, is first analyzed from a theoretical point of view. The related experiments are then reviewed: they include measurements of crystal shapes and of the facet dynamics. Finally, a few other experimental and theoretical works are presented. They mainly concern 3He crystals and 3He-4He mixtures for which a few dynamic properties such as growth resistances or heat transport through interfaces have been analyzed.