Vertex-corrected tunneling inversion in superconductors

Abstract

We have generalized the McMillan-Rowell tunneling-inversion program, which extracts the electron-phonon spectral function α2 F(Ω) and the Coulomb pseudopotentialμ * from experimental tunneling data, to include the lowest-order effect of vertex corrections. In so doing, the momentum dependence of the electron-phonon matrix elements are neglected, which is equivalent to using a local approximation. The vertex-corrected strong-coupling perturbation theory is performed on the imaginary axis and then an exact analytic continuation is used to produce the density of states on the real axis. Comparison with the experimental data for Pb indicates that effects of vertex corrections may be observable even in low-temperature superconductors.