Transition-metal monoxides: band or Mott insulators? Angle-resolved photoemission results for CoO

Evidence of itinerant band-like behaviour of the Co 3d states in paramagnetic CoO has been observed in CoO(001) angle-resolved photoemission spectra. Two d bands are identified, which disperse 0.4 eV and 1.7 eV between Gamma and X. In broad terms the results are consistent with a recently proposed model of the electronic structure in which the insulating gap arises largely from an exchange potential perturbation of the one-electron band structure.