ABSTRACT
This chapter focuses on the superconductive state. It is a worthy test to investigate how the excitonic Coulomb mechanism applies to the superconductive phase. Within the conventional wisdom and under the assumption that the cuprate Cooper pair is still a two-body entity, the two-particle pairing wavefunction or the superconducting order parameter can be expanded into eigenfunctions that form the irreducible representation of the Hamiltonian symmetry group. In the 1950s, B. T. Matthias developed a set of empirical rules outlining the superconductivity in the periodic table of elements, which are later conveniently referred to as Matthias rules. Graphite itself is well known to have both electrons and holes, though too many of which, according to the excitonic Coulomb model, are counterproductive to superconductivity. In a similar fashion, J. Hirsch’s hole superconductivity can now also be understood: the holes are effective in reducing electrostatic repulsion among electrons.
