Observation of superconducting gap in boron-doped diamond by   laser-excited photoemission spectroscopy
  We have investigated the low energy electronic state of a boron-doped diamond thin film by the ultrahigh resolution laser-excited photoemission spectroscopy. We observed a clear shift of the leading edge below 11 K indicative of a superconducting gap opening ($\Delta \sim 0.78$ meV at 4.5 K). The gap feature is significantly broad and the well-defined quasiparticle peak is not recognizable even at the lowest temperature of measurement 4.5 K. We discuss our result in terms of possible disorder effect on superconductivity in this system. 
K. Ishizaka, R. Eguchi, S. Tsuda, T. Yokoya, T. Kiss, T. Shimojima, T.   Togashi, S. Watanabe, C.-T. Chen, C. Q. Zhang, Y. T...