Spin dependent many-body effects in the photoemission of Co

Many-body effects influence the energy versus momentum relation that is measured in angle-resolved photoemission experiments and the quasi-particle band structure may be significantly different from what is deduced within the independent particle model. In the case of cobalt many body effects are even more drastic than an energy renormalization giving rise to a quenching of quasi-particle peaks. Augmenting ab-initio band structure with many-body e-e interactions, we have obtained spin- and k-dependent self-energies, hole spectral functions and quasi-particle energies to be compared with photoemission spectra; our results show that e-e correlations are responsible for strong spin-dependent energy renormalizations.