Phase Separation and Nucleation in Superfluid Mixtures of 3He–4He at Presence of a Heat Flow

Abstract

The kinetics of phase separation of superfluid 3He–4He mixtures heated from below is studied. Phase separation is registered by sharp change of concentration in different parts of a measuring cell. It is shown that separation is preceded with formation of a metastable supersaturated mixture, and a temperature gradient, under which phase transition starts, practically coincides with a critical temperature gradient for occurring the thermal instability. The obtained data can be explained in the frame of the model where nucleus of a new phase are formed on quantized vortices which attract 3He in their core. The attainable value of concentration estimated within this model of the supersaturated mixture is in rather good agreement with experimental data. At the same time it is not clear yet what among the processes starts first: phase separation or thermal instability.