High-resolution angle-resolved photoemission spectra from Ni(100): Matrix element effects and spin-resolved initial and final state bands

Abstract

We have carried out extensive one- and three-step angle-resolved photoemission spectroscopy (ARPES) intensity computations on Ni(100) within the band theory framework based on the local spin-density approximation. The results show a good overall level of accord with the recent high-resolution ARPES experiments on Ni(100) which probe the majority- and minority-spin ${\ensuremath{\Sigma}}_{1}$ band along the $\ensuremath{\Gamma}\ensuremath{-}K$ direction near the Fermi energy ${(E}_{F}),$ uncertainties inherent in our first-principles approach notwithstanding. The ${\mathbf{k}}_{\ensuremath{\Vert}}$ and energy dependencies of various spectral features are delineated in terms of the interplay between changes in the initial- and final-state bands and the associated transition matrix elements. The remarkable decrease observed with decreasing ${k}_{\ensuremath{\Vert}}$ in the ARPES intensity of the majority-spin ${\ensuremath{\Sigma}}_{1}$ band as it disperses below the ${E}_{F}$ as well as an enhanced spin polarization of the photoemitted electrons from the ${E}_{F}$ is shown to arise from the presence of a band gap in the final-state spectrum.