Superconductivity is a quality that designates those materials that , when cooled, stop exerting resistance and allow the passage of electric current without causing an energy loss.
Most superconductors work only at temperatures close to absolute 0. For decades, a material with these characteristics has been sought at room temperature. Now, thanks to a new study carried out by the Massachusetts Institute of Technology (MIT) in Cambridge, it has been discovered that graphene exhibits this same property.
Scientists say that having two layers of graphene one atom thick can turn the material into a superconductor . As they explain, the results suggest that it can conduct electricity in much the same way as known high-temperature superconductors (capable of conducting electricity without resistance around -140ºC maximum).
The discovery has been quite an event because, by eliminating the need for costly cooling, it could be able to revolutionize power transmission, the use of medical scanners and even transportation . And it is that it has impressive properties. Its sheets , for example, made of simple layers of carbon atoms arranged in hexagons , are stronger than steel and conduct electricity better than copper .
The latest studies suggest that the superconducting behavior of graphene is unconventional (since its activity cannot be explained by the dominant theory of superconductivity), and has a parallel with the activity observed in other unconventional superconductors, called ‘ cuprates’ .
The “magic angle”
Spanish physicist and project director Pablo Jarillo-Herrero of MIT and his team were not looking for superconductivity when working on their experiment, but were exploring how orientation, dubbed “the magic angle,” might affect graphene.
Theorists have claimed that offsetting the atoms between layers of 2D materials at this particular angle (1.1 °) could induce electrons (sliding through the sheets ) to interact in interesting ways .
The team immediately saw unexpected behavior in its two-leaf configuration. First, measurements of the conductivity of graphene and the density of the charge-bearing particles indicated that the construction had become a Mott insulator, that is, a material that has all the ingredients to conduct electrons, but whose interactions between the particles prevent them from flowing . The researchers then applied a small electric field to power extra charge carriers in the system, thus turning it into a superconductor.
The existence of an insulating state so close to superconductivity is a hallmark of unconventional superconductors like cuprates. The researchers saw patterns very similar to those seen for cuprates, providing further evidence that the materials may share a superconducting mechanism .
Thanks to this discovery, graphene-based devices will be easier to study than cuprates , making them useful platforms for exploring the secrets of superconductivity.
Reference: “Surprise graphene discovery could unlock secrets of superconductivity” Nature (2018) DOI: 10.1038 / d41586-018-02773-w
