High-resolution angle-resolved photoemission study of electronic structure and electron self-energy in palladium

In this study, we investigate the electronic structure and electron self-energy of palladium single crystals using polarization-dependent high-resolution angle-resolved photoemission spectroscopy. The observed Fermi surfaces and energy-band dispersions agree with those given by the band-structure calculation. A detailed comparison between the observed and theoretical band dispersions of the Sigma(1) band forming the electronlike Fermi surface indicates an electron-electron coupling parameter of lambda(ee) similar to 0.02. Near the Fermi level, a kink structure in the energy-band dispersion exists at similar to-20 meV, in agreement with the Debye energy. The electron-phonon coupling parameter is estimated to be lambda(ep) = 0.39 +/- 0.05 at 8 K for the Sigma(1) band, which is consistent with the theoretical values of lambda(ep) = 0.35-0.41. Furthermore, analyses of the self-energy indicate a possible contribution from the electron-paramagnon interaction in the energy range of -50 similar to -150 meV. The evaluated electron-paramagnon coupling parameter is lambda(em) similar to 0.06 for the Sigma(1) band. We found that the magnitudes of lambda(ep) and lambda(em) depend on the Fermi surface points. The total effective mass enhancement factor is estimated to be 1 + lambda(ep) + lambda(ee) + lambda(em) similar to 1.5 for the Sigma(1) band, which is close to the values m*/m(b) similar to 1.5-1.7 given by the de Haas-van Alphen and electron specific-heat measurements. DOI: 10.1103/PhysRevB.87.035140