Abstract
High-resolution angle-resolved photoemission spectroscopy (ARPES) using tunable synchrotron radiation has recently developed rapidly. New advances in high energy and angular resolution measurements enabled us to examine quantitatively fine spectral features near the Fermi level that are directly related to the low-energy excitation. We present a high-resolution ARPES study of an itinerant ferromagnet Ni. A kink structure was found in the dispersion of the minority-spin bands, while it was not clearly observed for the majority-spin band. On the basis of the self-energy analyses, the kink structure was attributed to the electron-phonon interaction. We found that the electron-phonon interaction and electron correlation contribute to the effective mass enhancement in a different way depending on the energy band, and spin-direction. The analyses is applicable to the surface derived-electronic states. In the case of Cu, the electron-phonon coupling constant was found to be equivalent at the surface and in the bulk.
