An effective 2-dimensional dynamic interaction potential was developed which embodied the screening of holes as carriers by charge density fluctuations and by optical phonons leading to superconductivity in magnesium diboride. The system was viewed as being an ionic solid containing B layers with holes as carriers in a unit cell and a polarization function was set up that fulfils the appropriate sum rules on the electronic and ionic polarizabilities. The value of the electron–phonon coupling strength and of the Coulomb screening parameter obtained from the static dielectric function within the 2-dimensional model indicated that the superconductor was in the strong coupling regime. The estimated superconducting transition temperature of MgB2 was about 43K and the pressure derivative of TC was negative. The isotope effect, coherence length, magnetic penetration depth and volume derivative of TC were also estimated to be consistent with the earlier results.

Superconducting Transition Temperature, Isotope and Pressure Effect in MgB2 - Phonon and Charge Fluctuation-Mediated Pairing Mechanism. D.Varshney, M.S.Azad, R.K.Singh: Superconductor Science and Technology, 2004, 17, 1446-57