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

摘要

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 Σ_1 band forming the electronlike Fermi surface indicates an electron-electron coupling parameter of λ_(ee) ～ 0.02. Near the Fermi level, a kink structure in the energy-band dispersion exists at ～-20 meV, in agreement with the Debye energy. The electron-phonon coupling parameter is estimated to be λ_(ep) = 0.39 ± 0.05 at 8 K for the Σ_1 band, which is consistent with the theoretical values of λ_(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 ～ -150 meV. The evaluated electron-paramagnon coupling parameter is λ_(em) ～ 0.06 for the Σ_1 band. We found that the magnitudes of λ_(ep) and λ_(em) depend on the Fermi surface points. The total effective mass enhancement factor is estimated to be 1 + λ_(ep) + λ_(ee) + λ_(em) ～ 1.5 for theΣ_1 band, which is close to the values m~*/mi, ～ 1.5-1.7 given by the de Haas-van Alphen and electron specific-heat measurements.