Mechanism of Superconductivity in Graphite-Alkali Metal Intercalation Compounds

Abstract

The mechanism of superconductivity in the first stage graphite-alkali metal intercalation compounds C₈M (M=K, Rb, or Cs) is investigated by the use of a method to solve the gap equation from the first principles. The observed transition temperature and anisotropy of the superconductivity can be explained well, when we consider that the three-dimensional alkali metal s-like electrons contribute to superconductivity with the aid of both the acoustic and the optic phonons in which the negatively charged carbon layers oscillate, respectively, in phase and out of phase with the positively charged alkali metal layers to give strong polar couplings with the electrons. The possibility of superconductivity in the two-dimensional graphite π-like electrons is also examined by the same method and found to be very small.