Reevaluating electron-phonon coupling strengths: Indium as a test case forab initioand many-body theory methods

Using indium as a test case, we investigate the accuracy of the electron-phonon coupling calculated with state-of-the-art ab initio and many-body theory methods. The ab initio calculations---where electrons are treated in the local-density approximation, and phonons and the electron-phonon interaction are treated within linear response---predict an electron-phonon spectral function α²F(ω) that translates into a relative tunneling conductance that agrees with experiment to within one part in 10³. The many-body theory calculations--- where α²F(ω) is extracted from tunneling data by means of the McMillan-Rowell tunneling inversion method ---provide spectral functions that depend strongly on details of the inversion process. For the most important moment of α²F(ω), the mass-renormalization parameter λ, we report 0.9±0.1, in contrast to the value 0.805 quoted for nearly three decades in the literature. The ab initio calculations also provide the transport electron-phonon spectral function αₜᵣ²F(ω) from which we calculate the resistivity as a function of temperature in good agreement with experiment.