Dominance of the final state in photoemission mapping of the fermi surface of Co/Cu(001)

The Fermi surface of tetragonally distorted fcc Co films grown on Cu(001) has been investigated with first-principles calculations and compared with an experimental determination using angle-resolved photoemission. The angular distributions for hnu=21-45 eV are dominated by the structure of the final states rather than by the shape of the Fermi surface. Theoretical estimates of the photoemission matrix elements support this observation. This suggests that photoemission can have limitations in mapping Fermi surfaces, especially for materials that exhibit flat, closely spaced valence bands.