IEEE Spectrum: Graphene is a very good conductor, and last year measurements of lithium-doped graphene showed hints that the substance could be a superconductor. Now, Takashi Takahashi of Tohoku University in Japan and his colleagues have developed a form of calcium-doped graphene that is a superconductor. Takahashi's team inserted calcium atoms between two sheets of graphene, forming C6CaC6. When the material was cooled to 4 K, its electrical resistivity dropped to nearly zero. Neither undoped bilayer graphene nor a lithium-doped version exhibited such low resistivity, which indicated that it was the addition of the calcium atoms that made the behavior possible. To find a version that works at a higher temperature, Takahashi says the group will test different doping metals and change the number and order of the graphene sheets.
