Abstract
The comparison study of high pressure superconducting state of recently synthesized H(3)S and PH(3) compounds are conducted within the framework of the strong-coupling theory. By generalization of the standard Eliashberg equations to include the lowest-order vertex correction, we have investigated the influence of the nonadiabatic effects on the Coulomb pseudopotential, electron effective mass, energy gap function and on the 2Δ(0)/T(C) ratio. We found that, for a fixed value of critical temperature (178 K for H(3)S and 81 K for PH(3)), the nonadiabatic corrections reduce the Coulomb pseudopotential for H(3)S from 0.204 to 0.185 and for PH(3) from 0.088 to 0.083, however, the electron effective mass and ratio 2Δ(0)/T(C) remain unaffected. Independently of the assumed method of analysis, the thermodynamic parameters of superconducting H(3)S and PH(3) strongly deviate from the prediction of BCS theory due to the strong-coupling and retardation effects.