Superconductivity in Hydrogenated Graphites

Abstract: We report transport and magnetization measurements on graphitic materials that have been hydrogenated after being treated with octane. The temperature-dependent electrical resistivity shows anomalies manifested as re-entrant insulator-metal transitions. Below 50 K, the magnetoresistance data shows both antiferromagnetic and ferromagnetic behavior as the magnetic field is decrease or increased, respectively. The system is possibly an unconventional magnetic superconductor. The irreversible behavior observed in the field-cooled vs. the zero-field cooled data for a sufficiently high magnetic field suggests that the system might enter a superconducting state below 50 K. Energy gap data is obtained from nonlocal electric differential conductance measurements. An exciton-based mechanism is likely driving the system to the superconducting state below 50 K, where the gap is divergent. We find that the hydrogenated carbon fiber is a multiple gap system with critical temperatures estimates above room temperature. The temperature dependence of the superconducting gap follows the flat-band energy relationship, with the flat band gap parameter linearly increasing with the temperature above 50 K. Thus, we find that either a magnetic or an electric field can drive this hydrogenated graphitic system to superconducting state below 50 K. In addition, AF spin fluctuations creates pseudo-gap states above 50 K.