On the Pressure Dependence of Electrical Conductivity of Graphite

Electrical conductivity (σ) of pyrolytic graphite along the basal was measured at room temperature in the presence of hydrostatic pressures ( p ) up to 20 kb. the pressure dependence coefficient d ln σ/d p evaluated was only order of 10 -3 /kb, despite compressive stresses gave rise to a suppression of lattice vibrations, and also to an increase of the carrier concentration ( N ) with a rate of d ln \(N/dp{}10⁻²\)/kb. Such a discrepancy has successfully been removed by taking into account the pressure-induced change of the effective mass of carriers, which functions so as to cancel the increment of σ due to the increase of N . Calculations were performed on the basis of an effective mass approximation for the Slonczewski-Weiss band model. Thus, the participation of carrier-carrier scattering proposed by Yeoman and Young is excluded from responsible mechanisms. Discussions given of the c -axis conductivity on the same basis have also yielded a success in accounting for the pressure dependence.