Critical Supersaturation of Superfluid 3He-4He Mixtures

We report the results of our systematic study of the phase separation in supersaturated 3He-4He liquid mixtures of the 3He-dilute phase. The amount of the critical supersaturation is determined within the wide ranges of the temperature (0.4–645mK) and the pressure (1–8.5kgf/cm2). Using the data we construct the surface of critical supersaturation, Δx3, cr(T, P), which enables us to recognize almost the overall behavior of the critical supersaturation in superfluid 3He-4He mixtures. The main specific features observed are (i) below ∼10mKΔx3, cr is almost temperature-independent, (ii) above ∼10mK up to ∼500mKΔx3, cr increases with the temperature, and (iii) above ∼500mKΔx3, cr decreases smoothly with the increase of temperature down to zero at the tricritical point. We give various discussions from the viewpoint of the quantum nucleation, the classical thermal nucleation and the crossover between them.