Novel many-body effects in the photoemission spectrum of ultrathin bcc-cobalt films

Exact calculated results of the photoemission spectrum of a two-layer {001} bcc-cobalt film are presented. Realistic band-structure results are used in the parametrization of the Hamiltonian in a periodic small-cluster approach. An intrasite electron-electron interaction fully allowed by atomic symmetry is introduced. Interesting new features induced by many-body effects are found in the calculated spectrum. Physical conclusions about the many-body states in ultrathin bcc-cobalt films are drawn. Surface-sensitive valence-band photoemission experiments are suggested to test our results.