Reevaluating electron-phonon coupling strengths: Indium as a test case for ab initio and many-body-theory methods

TL;DR

This study compares ab initio and many-body theory methods for calculating electron-phonon coupling in indium, finding ab initio results highly accurate and revealing a revised value for the mass-renormalization parameter lambda.

Contribution

It provides a detailed evaluation of electron-phonon coupling calculations using state-of-the-art ab initio and many-body methods, updating the lambda value and validating resistivity predictions.

Findings

Ab initio calculations match experimental tunneling conductance within 0.1%.

Many-body theory spectral functions depend heavily on inversion details.

Revised lambda value of 0.9 +/- 0.1 contrasts with historical 0.805.

Abstract

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 alpha^2 F(omega) which translates into a relative tunneling conductance that agrees with experiment to within one part in 1000. The many-body theory calculations -- where alpha^2 F(omega) 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 the most important moment of alpha^2 F(omega), the mass-renormalization parameter lambda, 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 alpha_{tr}^2 F(omega), from which we calculate the resistivity as a function of temperature in good agreement with experiment.