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Graphene is an incredible material. It is only one atom thick, but it is 200 times stronger than steel. It is a network of carbon atoms and can conduct electricity. Under the right conditions, it is a superconductor, so the electrical flow meets no resistance.
We only know the superconductivity of graphene since 2018. Two layers of graphene have been placed on top of each other. They weren’t perfectly stacked, they had a little twist of 1.1 degrees. The layers have been cooled slightly above absolute zero, and voila! Superconducting graphene.
As reported in Science, the new work added an extra layer of graphene. Superconductivity in this graphene sandwich is achieved at a slightly different twist angle (on average 1.56 degrees), but up to a higher temperature – although still only a few degrees above absolute zero. The result is interesting in itself, as we are learning more about graphene. However, this has wider implications. It allows researchers to study superconductivity in a completely new way.
The three-layer graphene superconductor is sensitive to an externally applied electric field. By adjusting the strength of this field, researchers can control the level of superconductivity in the system. Researchers now have a flexible way to study superconductivity.
“Superconductivity in twisted graphene provides physicists with an experimentally controllable and theoretically accessible model system where they can play with the properties of the system to decode the secrets of high temperature superconductivity,” said one of the lead co-authors of the article, Harvard University postdoctoral researcher Andrew Zimmerman, in a statement.
“It allowed us to observe the superconductor in a new dimension and provided us with important clues about the mechanism that drives superconductivity,” added the study’s other lead author, Zeyu Hao, also a PhD student at Harvard.
The holy grail of superconductivity is to create a superconducting material under ambient conditions. Last year, the first room-temperature superconducting material was announced, but it has few complications. It was just a small amount of material and to become a superconductor it had to be squeezed between two diamonds at a pressure of 2.5 million atmospheres. It really doesn’t scream “wonderful material that will change our lives.”
The new three-layer graphene has shown that its superconductivity is driven by a strong interaction between electrons. This mechanism is believed to be very important in creating stable high temperature superconductors, but they are not fully understood. This system could provide crucial insight into the theory of superconductivity.
“The more we understand, the more likely we are to increase superconducting transition temperatures,” Kim said.
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