Possibility of surface superfluidity in parahydrogen crystals
Abstract
This paper is an attempt to explain the recently observed phenomenon of gravity-induced flow of solid parahydrogen. The proposed explanation is based on the assumption that at temperatures below 3 K (when the flow effect is observed) the surface layers of the parahydrogen are superfluid. The superfluid surface phase resembles a two-dimensional phase and thus vortices are easily formed in it. In the presence of vortices the force of gravity causes a steady-state flow in the surface layer and the velocity of this flow determines the mass flow. The mass flow rate found within the framework of the model of a superfluid surface layer is of the same order of magnitude as that observed experimentally.