The nucleation of
B-phase from the super-cooled A-phase is a rather
complicated issue that has been under investigation for
several years by now without full clarification.
In our early work [PRL 54,
245 (1985)] we made experimental mapping on the
distribution of B-phase nucleation events in
temperature. According to Leggett [PRL 54,
246 (1985)], our results can be reconciled with the
baked Alaska model, according to which the formation of
the B-phase is triggered by a cosmic ray.
FIGURE (a) Supercooling of the A-phase into the B-phase as a function of pressure. (b) Observed nucleation events (histogram) at 29.3 bars are inconsistent with the original baked Alaska model [PRL 53, 1096 (1984)] that yields P(T) ~ (1-T/Tc)3.