Supercooling of the A phase of 3He
Yefan Tian, Dmytro Lotnyk, Anna Eyal, Kuang Zhang, Nikolay Zhelev, T. S. Abhilash, Aldo Chavez, Eric N. Smith, Mark Hindmarsh, J. Saunders, Erich J. Mueller, J. M. Parpia
Abstract
Abstract Because of the extreme purity, lack of disorder, and complex order parameter, the first-order superfluid 3 He 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 3 He can be exploited to model transitions in the early universe.