Supercooling of the A phase of 3He

Because of the extreme purity, lack of disorder, and complex order parameter, the first-order superfluid He-3 A-B transition is the leading model system for first order transitions in the early universe. Here we report on the path dependence of the supercooling of the A phase over a wide range of pressures below 29.3 bar at nearly zero magnetic field. The A phase can be cooled significantly below the thermodynamic A-B transition temperature. While the extent of supercooling is highly reproducible, it depends strongly upon the cooling trajectory: The metastability of the A phase is enhanced by transiting through regions where the A phase is more stable. We provide evidence that some of the additional supercooling is due to the elimination of B phase nucleation precursors formed upon passage through the superfluid transition. A greater understanding of the physics is essential before He-3 can be exploited to model transitions in the early universe. The A-B transition in superfluid He-3 is a pure experimental model system to study first-order phase transitions in the early Universe. Tian et al. observe the path dependence of the supercooling of the A phase in a wide parameter range and provide explanations for the heterogeneous nucleation of the B phase.

Automated summary

Due to its extreme purity, lack of disorder, and complex order parameter, the first-order superfluid He-3 A-B transition is considered as a leading model system for first order transitions in the early universe. In this study, the path dependence of the supercooling of the A phase is reported over a wide range of pressures below 29.3 bar at nearly zero magnetic field. It is found that the metastability of the A phase is enhanced by transiting through regions where the A phase is more stable, resulting in additional supercooling due to the elimination of B phase nucleation precursors formed upon passage through the superfluid transition.