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Light Weight Superconductors

Light Weight Superconductors

Interesting story over at Physical Review Focus on new superconducting wires that are light weight, incredibly strong and, being superconductors, carry current with no resistance.

There are two points of interest in this article. First, is the practical aspect. These wires can carry incredibly large currents, which in turn are capable of producing very high magnetic fields. They are also incredibly strong, potentially “stronger than steel”. This means if you want a superconducting device you can build it entirely from these wires, and you don’t need a heavy steel frame as well. Why is all this of interest? Among the probably many reasons is thatthese are all conditions that are needed “in several futuristic spacecraft propulsion systems”, i.e., being light and strong but capable of producing high magnetic fields. I’m not sure what these systems involve, though – have to get back to you on that one!

The second main point is of theoretical interest, namely, what makes materials superconduct? Superconductivity in simple materials, such as lead, is well understood. Materials have resistance because when electrons try and flow through the material, they collide with other atoms and lose energy (just like trying to run through a crowded room – you keep hitting people and having to start again.) When cooled to almost absolute zero, however, electrons in certain metals pair together in what’s known as Cooper pairs. These pairs of electrons are then able to move through the metal while dodging all the other atoms. There’s no good analogy for this, really – it’s a quantum mechanical effect and most of our usual intuition doesn’t apply. Just be impressed that this is quantum mechanics on the macro scale – working in every day life!

What we don’t understand is high temperature superconductors, which superconduct at around 100 degrees above aboslute zero (-173 degrees Celcius, give or take.) According to the original theory, the comparitively high temperatures would destroy the superconductivity. We don’t have a good theory yet to explain what’s going on, and many groups, including ours at the University of Queensland, are working to understand it. The material these wires are made out of is similar to these high-T superconductors (it can’t be explained by the original supercondtivity theory) but the material issimpler, which might mean researchers can use it to understand what’s going on in all the materials. A successful theory might mean we could build better and cheaper superconductors, perhaps even ones capable of working at room temperature!

For more info on superconductors, check out superconductors.org for a good general overview, or for a slightly more advanced treatment, there’s the ever-faithful Wikipedia. And, of course, Google searches turn up many links!

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