Reproducible tunneling determination of the electron-phonon spectral function in optimally-doped Bi-2212 single-crystal break junctions

In this article we describe the reproducible determination of the electron density of states (DOS) of Bi2Sr2CaCu2O8+x (BSCCO) we recently obtained by applying an unfolding procedure to the tunneling dI/dV data of break juncti ons made in single crystals with T-c = 93 +/- 2 K. The main result is the r eproducible determination of the electron-phonon spectral function alpha(2) (omega)F(omega) of BSCCO from seven different curves by using the standard program for the inversion of the Eliashberg equations (EE) and by taking in to account an appropriate energy dependence of the normal DOS. The coupling constant lambda, calculated consistently with the presence of the energy-d ependent normal DOS, shows values between 1.9 and 2.7. The consequences of d-wave pair symmetry in the direct solution of the EE with reference to our experimental data are also discussed. (C) 1998 Elsevier Science Ltd. All r ights reserved.