ANALYSIS OF THE SUPERCONDUCTING TRANSITION-TEMPERATURES PRESSURE-DEPENDENCE FOR YBA2CU3O7-DELTA WITHIN A BCS FRAMEWORK

The pressure dependence of the superconducting transition temperature dT(c)/dP of the YBa2Cu3O7 high-T-c superconductor is addressed. A valu e of dln T-c/dln V (where V is the volume) comparable to the phonon Gr uneisen parameter is revealed, thereby allowing for reasonable analysi s using the Allen-Dynes equation for T-c. The electronic contribution to the electron-phonon coupling parameter eta is found to be positivel y influenced by pressure, with a volume dependence of dln eta/dln V ap proximate to -3, and to offset the Gruneisen parameter's contribution in the equation for dln T-c/dln V by about a factor of 1.5 thus result ing in a positive pressure dependence of T-c. This value is comparable to that observed in conventional superconductors. The possible influe nce of a van Hove singularity near the Fermi energy on T-c(P) results is discussed.