Engineering news
Researchers at the University of Cambridge have found a way to activate the innate, but previously hidden, ability of graphene to act as a superconductor, meaning that it can be made to carry an electrical current with zero resistance.
Graphene is a two-dimensional sheet of carbon atoms and combines several properties, such as being very strong, but also light and flexible, and highly conductive.
Until now, superconductivity in graphene has only been possible by doping it with, or by placing it on, a superconducting material, a process which can compromise some of its other properties.
Researchers managed to activate the dormant potential for graphene to superconduct in its own right by coupling it with a material called praseodymium cerium copper oxide (PCCO).
PCCO is an oxide from a wider class of superconducting materials called ‘cuprates’. It also has well-understood electronic properties, and using a technique called scanning and tunnelling microscopy, the researchers were able to distinguish the superconductivity in PCCO from the superconductivity observed in graphene.
Superconducting graphene could be used to create superconducting quantum devices for high-speed computing or prove the existence of a mysterious form of superconductivity known as "p-wave" superconductivity, which academics have been struggling to verify for more than 20 years.
Dr Jason Robinson, a fellow of the university, 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?"
Similar approaches have been taken in previous studies using metallic-based superconductors, but with limited success. Placing graphene on metal has resulted in change of properties and the superconductive activity originates from the metal rather than the graphene.
Superconductivity is characterised 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.
During the experiments, the researchers observed that the graphene’s electron spin state was vastly different from that of the PCCO, indicating that the superconductivity was not coming from the graphene rather than the PCCO.
The study suggests that the researchers activated the "p-wave" form of superconductivity, but further research needs to be conducted to substantiate the claim.
The study suggests that graphene could be used to make a transistor-like device in a superconducting circuit, and that its superconductivity could be incorporated into molecular electronics, given the variety of chemical molecules that can bind to graphene's surface.
Superconductors are used in numerous applications because they generate large magnetic fields they are an essential component in MRI scanners and levitating trains. They could also be used to make energy-efficient power lines and devices capable of storing energy for millions of years.
The findings were reported in the journal Nature Communications.