In the cold, gad medium of helium-3 excess fluid, scientists recently made an unexpected discovery. Foreign objects traveling through the medium can exceed critical speed limits without breaking the delicate excess fluid.
As opposed to our understanding of this excess fluid, it presents quite a puzzle – but now, by recreating and studying the phenomenon, physicists have discovered how it happens. Excessive fluid particles stick to the object, preventing it from interacting with bulk excess fluid, thus preventing the breakdown of excess fluid.
“Superfluid helium-3 feels like a vacuum to the rod passing through it, although it is a relatively gaseous liquid. There is no resistance, nothing at all,” said Samuli Titi, a physicist at Lancaster University in the UK. Was. “I find this very interesting.”
Superfluids are a type of liquid that has zero viscosity and zero friction, and therefore kinetic energy flows without losing energy. They can be formed relatively easily from the bosons of the helium-4 isotope, which, when cooled above absolute zero, slow down enough to overlap and form a high-density cluster of molecules acting as a ‘super-atom’.
However, these ‘super atoms’ only make one kind of excess fluid. The second is based on Boson’s brother, Fermien. Fermions are particles that contain molecular building blocks such as electrons and quarks.
When cooled below a certain temperature, the fermen are bound to each other in what are called cooper pairs, each made up of two fermions that together form a boson. This Cooper pair behaves exactly like bosons and thus creates redundant liquids.
The team created their fermionic superfluid outside of helium-3, a rare isotope of helium missing a neutron. When cooled to tens of thousands of degrees above absolute zero (0.0001 Kelvin, or -273.15 degrees Celsius / -459.67 degrees Fahrenheit), helium-3 forms Cooper pairs.
This excess fluid is very fragile, and the Cooper pair can break if an object moves through it at a certain velocity, called a complex ground velocity.
And yet, in a 2016 paper, researchers at the University of Lancaster discovered that helium-3 could exceed this velocity without breaking the wire rod passing through the superfluid.
In their follow-up experiments, they measure the force required to move the wire rod through excess fluid. When the wire starts moving they measure a very small force, but once it moves forward, the pressure required to continue was zero – just give it a nudge and it goes.
The team concluded that the initial force comes around a bit to accommodate the motion from the Cooper pair, employing that small initial force on the wire rods. But, after that, the wire can move freely, essentially hidden in the coat of the Cooper pairs.
“By changing the direction of the rod’s motion, we were able to conclude that the rod would be obscured by excessive liquid by bound particles covering it, even if its speed was too high.”
There may be some interesting effects in this new discovery.
Fermionic superfluids can be used to make superconductors, which in turn are under investigation as a critical component of quantum computers. Knowing more about how and why excess fluid works is likely to only bring us closer to that goal.
Research has been published in Nature Communications.
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