Loss of memory in 'dirty' superfluid 3He

The transition between the A and B superfluid phases of He-3 is first order, and the A-phase has been known to supercool far into the region where the B-phase is thermodynamically stable. The extent of the supercooling strongly depends on whether the cooling originates from above, or from below the normal-to-superfluid transition. For the latter, the supercooling has a 'memory' of the prior warming history. We have studied the nucleation of the B-phase for pure He-3 and for a superfluid constrained to a dilute silica aerogel of 98% porosity. Interestingly, we have found that the nucleation of the aerogel B-phase shows, unlike the pure case, no memory, even though large supercooling of the aerogel A-phase is observed. (C) 2003 Elsevier Science B.V. All rights reserved.