The "wonder material" graphene has another significant quality to add to its impressive list of electrical and mechanical properties: superconductivity. Physicists in Canada and Germany have shown that graphene turns into a superconductor when doped with lithium atoms – a result that could lead to a new generation of superconducting nanoscale devices.
Graphene exhibits a range of remarkable properties, thanks to its special structure – a one-atom-thick hexagonal lattice of carbon atoms. It is far stronger than steel while also flexible, and is an excellent conductor of both electricity and heat. In its pristine form, however, it is not a superconductor.
Neither is pure graphite, but in 2005 physicists showed that graphite could be made to superconduct when chemically treated, so as to create bulk materials consisting of graphene alternated with one-atom-thick layers of another element. The best performing material thus created, calcium graphite (CaC6), has a superconducting transition temperature of 11.5 K. Theorists identified the underlying mechanism for that superconductivity as electron–phonon coupling. Phonons are vibrations in a material's crystal lattice that bind electrons together into "Cooper pairs" that can travel through the lattice without resistance – one of the hallmarks of superconductivity. It was then realized that such electron–phonon coupling might occur not just in bulk graphite compounds but also by depositing atoms of a suitable element on to single layers of graphene.
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