VERTEX-CORRECTED TUNNELING INVERSION IN ELECTRON-PHONON MEDIATED SUPERCONDUCTORS - PB

The McMillan-Rowell tunneling inversion program, which extracts the el ectron-phonon spectral function alpha(2)F(Omega) and the Coulomb pseud opotential mu from experimental tunneling data, is generalized to inc lude the lowest-order vertex correction. We neglect the momentum depen dence of the electron-phonon matrix elements, which is formally equiva lent to using a local approximation. The perturbation theory is perfor med on the imaginary axis and then an exact analytic continuation is e mployed to produce the tunneling density of states on the real axis. C omparison is made with the experimental data for Pb. We find lambda is increased by approximately 1% due to the vertex corrections.