Ultraviolet photoemission study of CaVO3

The electronic structure of CaVO3 is studied on single-crystalline samples cleaved in ultrahigh vacuum by means of ultraviolet photoelectron spectroscopy (UPS). In the UPS spectra of the V3d-band region, a sharp peak near the Fermi level (EF) and a broad one centered at 1.4 eV below EF are shown. The former is assigned to the coherent band, whereas the latter is to the precursor of the lower Hubbard band, or the incoherent band. As the cleaved surfaces are exposed to oxygen, the ratio of the spectral weight of the coherent band to that of the incoherent band increases. At the same time, the spectral width of the coherent band enlarges. We conclude that the UPS spectra of the cleaved surfaces are partially caused by the electronic structure characteristic of the surface for which the correlation effect is expected to be more profound compared with that for the bulk.