Liquid Helium: That Super Fluid!

Who hasn't tried inhaling some Helium from a balloon? I'm sure you sounded amazing, and no i'm not calling for any Mariah Carey voice samples from you :D

Well, Helium's fascinating and weird things don't stop there, in fact, it's about to get weirder ..

How does Helium become a superfluid?

Basically, when Helium is cooled down to an extreme level (known as cryogenic temperatures) reaching slightly below its boiling point at –269°C / –452.2°F / 4 K (I know we're used to boiling point meaning HOT, but in the case of helium, it is quite the COLD temperature, at least for us humans - since essentially boiling point is the state at which an element turns into gas), at this stage it will turn into this superfluid state.
This actually applies only to helium-4 (at 2.17 K) and helium-3 (at 0.025 K for stage A and 0.001 K for stage B) among all Helium isotopes.

Superfluid transition for Helium-4

Superfluid transition for Helium-3: Notice there are 2 superfluid stages A and B. The difference is essentially is with spin-ordered and spin-disordered structures

Lambda state (which takes its name after the lambda Greek letter λ ) showing the heat capacity of Helium-4 compared to temperature at 2.17 K

So, now Helium is in a superfluid state, what does it mean? and what's so super about it?

Effectively, at this stage, Liquid Helium is capable of, take a deep breath, the following:

It now has ZERO viscosity, meaning it flows without any friction over any surface, and hence without any loss in its kinetic energy (with a critical velocity of around 20 cm/s).
It can now defy gravity and climb through its containers' walls, but also flow through pores in its containers, pores as thin as a molecule (pore diameter equal or above to 0.7 nm)
If you spin your tea, step away for a minute or so, and it would have settled. For Super Helium, If spun, it would continue to spin indefinitely
While its container is being spun, super helium would also weirdly stay motionless.
Heating up a capillary tube in contact at the bottom with helium would cause the superfluid to squirt like a fountain.

Illustration of Helium flowing over surfaces

Image of Helium creeping over the sides of its container, and then causing a dripping drop that falls below. Eventually all Helium will evade the container

Illustration of Heated Helium Fountain Effect

Why does it act as such?

Essentially it is due to the Bose-Einstein Condensation. (Einstein must be lingering somewhere near these cool thing)
The fact that Helium remains liquid down to absolute ZERO Kelvin, temperature at which atoms conceptually halt movement, yet its particles still jiggle with zero-point motion. With this in mind, the particles overlap so as they behave as a single particle and can no longer be identified as separate entities, they become in a state of unison. They are essentially, in a better term, quantum entangled.

Is it the only superfluid?

Several experiments have been conducted on ultracold fermionic gases, particularly Lithium-6 and earlier on Rubidium-87 which exhibited quantum vortices, a qualifying property of superfluids.
It is also speculated that this property would exist in neutron stars, due to their nucleons' high density and low temperature .

Usefulness of superfluids?

Besides being weird and cool, one of their uses is as a quantum solvent, whereby they allow any molecule placed within, to behave as if it was within a gas phase.
They are also essentially used in high-precision gyroscopes.
One amazing experiment conducted in 1999 allowed the use of one superfluid to greatly reduce the speed of light, through the use of Sodium gas, resulting in slowing it down to a crazy 17 m/s. This is not common to all superfluids though.

Liquid Helium as a Coolant

Helium in particular is also used for several key industry needs, with one key application is being used as a coolant in liquid form for MRI scanners' coils, due to the extensively low temperature in liquid form, allowing then the generation of magnetic fields responsible for the actual MRI imagery.

You can also enjoy an excellent video about super helium - extracted from a BBC documentary

And another video with the fountain effect

So next time you try to play with Helium Balloons, just keep in mind, Liquid Helium is way cooler than that .. literally !

Thank you for reading through

@mcfarhat

References:

Photo Credits:

Image 1: CC images available online via google, labeled for reuse with modifications, edited and combined by yours truly:)
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