Separate Phases In Superfluids

Superconductivity is something most people are willing to accept without question. Why shouldn’t it be possible for electrons to move through a metal without encountering resistance? This is probably because electricity is quite an abstract thing, we can’t see it and most of the time its presence isn’t noted. Something that makes people uncomfortable, however, is the concept of a superfluid. A superfluid is a liquid which experiences no loss of kinetic energy while flowing and has a viscosity of zero. Even air has a viscosity of 1.81×10P (poise, named after Jean Poiseuille). If you do a single stir in vat of superfluid it will continue to circle forever like the never diminishing current in superconductors.

Diagram by Julio Reis

The picture above shows another property of superfluids, they are more determined then their normal counterparts to become level and so will creep over the walls of the central container until their is a uniform level throughout the system.

Helium is the most common element that gets turned into a superfluid. Helium-4, most often, as it forms a superfluid at a greater temperature and has the unique aspect of each individual helium being a boson instead of a fermion. But research performed on helium-3 has showed that there are in fact two different states in the helium-3 superfluid, labelled A and B unsurprisingly. B phase was the generally more stable of the two and is the superfluid that most research has been done on in the past. But when the temperature or pressure starts getting raised to the point where superfluidity might be lost, the helium-3 undergoes a phase change and it is the A type that is more stable in these conditions.



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