Peculiarities of the Electron-Phonon Interaction in Graphite Containing Metallic Intercalated Layers

The calculation of the local density of electronic states of graphene with vacancies, using the method of Jacobi matrix, was performed. It was shown that for atoms in the sublattice with a vacancy the local density of electronic states conserves the Dirac singularity, similarly as in an ideal graphene. A quasi-Dirac singularity was observed also in the phonon spectra of graphite for the atom displacements in the direction perpendicular to layers. Changes of phonon spectra of graphite intercalated with various metals were analyzed. On the basis of our results and using the BCS theory and Eliashberg equation we proposed what dynamic properties an intercalated graphite system should show to obtain an increased Tc.

PRESSURE COEFFICIENT OF THE SUPERCONDUCTING TRANSITION TEMPERATURE IN THE STRONG COUPLING LIMIT

Pressure coefficient (β) of the superconducting transition temperature (T c ) for a two dimensional system is studied in presence of Coulomb interaction, using Eliashberg equation with the Einstein approximation for the phonon system, within the van Hove scenario. β is found to be high in the low-T c region and low in the high-T c region. β is positive in the underdoped region and becomes negative in the overdoped region. For a given value of Fermi energy, β increases in the underdoped region and decreases in the overdoped region with the increase of Coulomb repulsion.