ELIASHBERG EQUATIONS WITH ENERGY-DEPENDENCE OF THE NORMAL DENSITY-OF-STATES AND QUASI-PARTICLE TUNNELING IN HIGH-T-C SUPERCONDUCTORS

In the present paper the limits and the correct utilization of the sta ndard program for the inversion of Eliashberg equations for the determ ination of the electron-phonon spectral function in high-T-c supercond uctors are discussed. In order to compare the calculated density of st ates with the experimental one that we recently measured in Bi2Sr2CaCu 2O8+x single-crystal break junctions with T-c = 93K, we introduced the results of the standard inversion procedure in a direct program for t he solution of Eliashberg equations. We explain most of the observed d ifferences between theoretical and experimental curves at energy great er than the gap by a smooth energy dependence of the normal density of states that we introduced in the direct solution of the Eliashberg eq uations. The effects of the energy-dependent electron-phonon spectral function on the quasiparticle density of states are also presented in a simple particular case.