Graphene promising as superconductor
Graphene is super light, flexible, very strong and a good conductor. But now the wonder carbon graphene, seems to reach the holy grail: superconductivity.
For the first time, Cambridge researchers have shown that graphene (only one atomic layer) is able to pass electric current without any resistance.
Cambridge In an article in the journal Nature Communications, the researchers have written that such superconducting graphene can open interesting practices for energy-efficient and very fast nano-electronica. For now it is a principle: the new quality occurs in rather impractical temperatures: far below freezing point.
In 2004, graphene has been discovered by the Dutch Russian professor Andrei Geim. For a long time, graphene has been promising as potential superconductor, but so far, researches failed.
In recent years Japanese researchers found superconducting graphene as it was processed with calcium, or covered with lithium.
The problem was that the other super qualities of the graphene then seemed to be lost.
It’s official: graphene has been made into a superconductor in its natural state – which means electrical current can flow through it with zero resistance.
Last year, physicists managed to do this by doping graphene with calcium atoms, but this is the first time researchers have achieved superconductivity in the material without having to alter it. The results so far show that the material achieves an incredibly rare type of superconductivity that’s even crazier and more powerful than scientists expected.
Couple graphene to a superconductor
“It has long been postulated that, under the right conditions, graphene should undergo a superconducting transition, but can’t,” Robinson said. “The idea of this experiment was, if we couple graphene to a superconductor, can we switch that intrinsic superconductivity on? The question then becomes how do you know that the superconductivity you are seeing is coming from within the graphene itself, and not the underlying superconductor?”
But in the new study, researchers at the University of Cambridge managed to activate the dormant potential for graphene to superconduct in its own right. This was achieved by placing the graphene on a material called praseodymium cerium copper oxide (PCCO).
It is superconductive at 4 degrees above absolute zero, but the graphene layer behaves differently as a conductor than in the more casual brittle material underneath.
Superconductivity is characterized by the way the electrons interact: within a superconductor electrons form pairs, and the spin alignment between the electrons of a pair may be different depending on the type – or “symmetry” – of superconductivity involved. In PCCO, for example, the pairs’ spin state is misaligned (antiparallel), in what is known as a “d-wave state”.
Remarkably, but whether this is an important insight? We have to wait according to Joost Frenken, professor at the ARCNL lab in Amsterdam.
Something for the foodies, I think for now. The suggestion that the super conductivity of graphene soon would appear at higher temperatures, he calls exaggerated.
Still, it’s attractive
Still the dream of superconducting graphene is attractive.
- The way in which the electrons are acting in the graphene network includes that they behave as particles without mass. As a result, they can easily move through the network as electric current.
- A superconducting phase would not only make the signals faster, it would be a hundred percent without any loss as well.
Classical superconductors are already widely used: for example in the refrigerated electromagnetic ingredients of MRI scanners. They are super-conducting at low temperature, forming the electron pairs which undisturbed dance through the material.
Superconductivity also occurs in some intricate ceramic substances. Sometimes even in less extreme low temperatures.
At room temperature, it is still not approved as superconductor.
Anyway graphene is promising. It is now used in some touch screens. Billions of dollars are spent on industrial and fundamental researches worldwide.
The research was led by Dr Angelo Di Bernardo and Dr Jason Robinson, Fellows at St John’s College, University of Cambridge, alongside collaborators Professor Andrea Ferrari, from the Cambridge Graphene Centre; Professor Oded Millo, from the Hebrew University of Jerusalem, and Professor Jacob Linder, at the Norwegian University of Science and Technology in Trondheim.
- P-wave triggered superconductivity in single layer graphene on an electron-doped oxide superconductor, Nature Communications, DOI: 10.1038/NCOMMS14024
- Graphene becomes superconductive—Electrons with ‘no mass’ flow with ‘no resistance’ phys.org
- Graphene and 2D Materials in the Press
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