FIGURE 1: MAGNET HOVERING ABOVE A SUPERCONDUCTOR COOLED WITH LIQUID NITROGEN

High Temperature Superconductors

You’re walking through a bustling city; the pandemic is over after using ultra-high-speed supercomputers to simulate vaccination effects; suddenly something whooshes over the bridge above you, a maglev train, travelling at 375mph; you arrive at work, a Mega Structure, step on the elevator and within seconds you’re at your 163 floor office.

This futuristic scene may be possible soon by finding materials able to exhibit superconducting properties, and in the case of maglev trains, these are already “flying” along in China!

Superconductors are materials which carry an electrical current with little to no resistance and exhibit the Meissner effect, where the superconductors expel their magnetic field from inside the material, creating a strong magnetic field outside. Superconductors have a critical temperature at which they transition from their usual state to a superconducting state. Another exciting property is a persistent current; using a ring of superconducting material and Lenz’s Law we can create a current which could run perpetually without the need for an external energy source!

They are used in MRI and NMR (Nuclear Magnetic Resonance) machines; the LHC (Large Hadron Collider), to accelerate charged particles to very large speeds; removal of land mines by detecting very weak magnetic fields and many other applications. Now, “electric grids, such as high-power lines, lose over 5% of their energy in the process of transmission”, which is a huge amount that could be reduced to 0 by using superconductors.

However, the main obstacle was that superconductors were only able to function at temperatures close to absolute 0, 0K, -273.15°C, which needed to be cooled with liquid Hydrogen. The race was on to find a material that could superconduct at temperatures above 63K so it could be cooled by liquid Nitrogen, a much more common resource.

In 1986 Bednorz and Miller made a breakthrough which put a new burst of energy into the race, they used an oxide material which was an insultor and never considered to be able to display superconducting properties! It was this out-of-the-box thinking and inspiration that led them to win the Nobel Prize in Physics in 19871. The compound was able to super conduct at 30K which got a team at the University of Alabama thinking. They switched Lanthanum to Yttrium making it possible for the compound to superconduct at temperatures just above 92K, therefore it could easily be cooled by liquid nitrogen!

Since then we have found more and more materials that superconduct but have not hit room temperature just yet. In late 2019, Lanthanum Decahydride LaH10 was recorded to superconduct at 260K but needs to be extremely highly pressurised. The closer we get to a room temperature superconductor at ambient pressure, the closer we get to saving billions on the loss of energy in the transfer of electrcity.

References

1. https://www.nobelprize.org/prizes/physics/1987/press-release/

2. https://phys.org/news/2016-06-maglev.html

3. https://www.britannica.com/science/Meissner-effect

4. https://www.rsc.org/Education/Teachers/Resources/Inspirational/resources/4.5.2.pdf

5. https://phys.org/news/2019-11-thorium-superconductivity-scientists-high-temperature-superconductor.html

6. https://www.electrical4u.com/properties-of-superconductors/

7. https://phys.org/news/2020-06-physicists-room-temperature-superconductors-revolutionize-world.html