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‘Magic angle’ twisted three-layer graphene not only has an incredibly exotic name, it could be a particularly rare type of superconductor, new research finds, that could be useful everywhere from medical equipment to quantum computers. .
Scientists are finding that stacking single atom graphene layers on top of each other at slightly different angles can create new materials with exciting properties, which led to the recent discovery of magically angled twisted three-layer graphene.
Now, a new study from the same team shows that this material could be a “spin-triplet” superconductor – which is unaffected by high magnetic fields – which makes it potentially even more useful.
“The value of this experience is what it teaches us about fundamental superconductivity, about how materials can behave, so that with these lessons learned, we can try to design principles for other materials that would be easier to manufacture, which could possibly give you better superconductivity, ”says physicist Pablo Jarillo-Herrero, of the Massachusetts Institute of Technology (MIT).
Superconducting materials are in high demand: they can conduct electricity without losing heat, which could revolutionize our power grids, portable gadgets, and more – if we ever get them to operate at normal temperatures.
Usually, electrons in superconductors couple in what are called Cooper pairs – each with opposite spins (one up and one down), traveling through the material like bound passengers on an express train. .
This is the conventional spin-singlet configuration anyway. However, the rare types of superconductors are the spin-triplet, which means that electrons have the same spin. Importantly, it means that a high magnetic field does not derail our imaginary express train, because the energy of the two electrons is moving in the same direction.
Through a series of experiments, the team were able to show that the magically angled twisted three-layer graphene continued to behave as a superconductor at magnetic fields greater than 10 Tesla, which is three times more than one might expect. expect from a single spin material.
In addition, the superconductivity disappeared and then returned as the strength of the magnetic field increased.
“In single spin superconductors, if you kill superconductivity, it never comes back – it’s gone for good,” says physicist Yuan Cao of MIT. “Here he reappeared again. So that makes it clear that this material is not a spin-singlet.”
The case is not yet closed – more research will be needed to verify the spin states of the electrons in this particular type of graphene. What we can say, however, is that the first results are very promising and very exciting for scientists.
One area where spin triplet superconductors could be useful is in MRIs: if these machines could operate under higher magnetic fields, they could produce much more detailed images. For now, however, ultra-low temperatures in the laboratory are still required for the material to act as a superconductor.
The material and its rare properties also hold promise for future research in quantum computing. A key problem in realizing the promise of practical and accessible quantum computers is to improve their stability – something that spin-triplet superconductors of some type could help.
“We have no idea if our type is that type,” Jarillo-Herrero explains. “But even if it doesn’t, it could make it easier to combine three-layer graphene with other materials to engineer this kind of superconductivity. It could be a major breakthrough. But it’s still very early days.”
The research was published in Nature.
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