Superconductivity of a Calcium-Doped Graphite CaC30

Granular superconductivity at room temperature in bulk highly oriented pyrolytic graphite samples

“…In spite of a small superconducting yield, too small to get any information about the corresponding superconducting phase(s), the observed behavior resembled the one expected for a system of Josephson coupled superconducting grains with critical temperature above room temperature [32]. These last results support earlier reports on the existence of room-temperature superconductivity in disordered graphite powders [33,34] and in HOPG samples [4,10].…”

“…1 crystallites. According to [46] diffraction peaks at 43.45 • and 46.32 • were found in graphite bulk samples, which can be ascribed to (10)(11) and (10)(11)(12) reflections of rhombohedral phase in coexistence within the hexagonal crystalline phase matrix. For our samples and within experimental resolution no diffraction peaks at those angles are observed indicating that the amount of rhombohedral phase should be much smaller than 1%.…”

Superconducting Behavior of Interfaces in Graphite: Transport Measurements of Micro-constrictions

“…Future experiments should try to increase the carrier density in a way that the coupling between graphene layers remains weak enough, as might be the case with hydrogen doping. Recently published measurements of Ca-doped graphite in the near surface region of oriented samples revealed hints for a transition at temperatures as high as 250K [22], supporting the idea that "hot-temperature superconductivity" [23] in graphite may be possible.…”

Experimental Study of the Intrinsic and Extrinsic Transport Properties of Graphite and Multigraphene Samples

“…The interfaces observed by TEM might then be the regions where enough carrier density exists to trigger quasi-two dimensional superconductivity. In contrast to the basically 3D superconductivity in intercalated graphitic compounds (Csányi et al, 2005) we expect that superconductivity at quasi-2D graphite interfaces as well as at doped surfaces (Han et al, 2010) may exist at much higher temperatures, partially because of the role of the high-energy phonons in the 2D graphite structure itself (García & Esquinazi, 2009). Room temperature superconductivity with a d + id pairing symmetry has been predicted to occur in doped graphene with a carrier concentration n 10 14 cm −2 (Pathak et al, 2010).…”