Eliashberg equations, pair symmetry and tunnel density of states in the optimally-doped high-T-c superconductor Bi2Sr2CaCu2O8+x

In this work, in order to compare the theoretical density of states (DOS) t o the tunneling data in the optimally-doped high-T-c superconductor(HTS) Bi 2Sr2CaCu2O8+x, we calculate the real-axis direct solution of the d-wave equ ations for the retarded electron-boson interaction in presence of half-fill ing and impurities. The use of a spectral function containing an isotropic part alpha(s)(2)F(Omega) and an anisotropic one alpha(d)(2)F(Omega) and the simple assumption: alpha(d)(2)F(Omega) = g(d)alpha(s)(2)F(Omega) where g(d ) is a constant leads, for appropriate values of the isotropic coupling con stant lambda(s) and the anisotropic one lambda(d), to solutions with only d -wave symmetry for the order parameter Delta(omega) and only s-wave one for the renormalization function Z(omega), The results properly fit both the c ritical temperature and the DOS in the whole energy range, as recently dete rmined in our break-junction tunneling experiments, but appear unable to do the same in the case of recent STM data. (C) 1999 Elsevier Science B.V. Al l rights reserved.