Underestimating the width of the bandgap in the electronic spectra of La₂CuO₄

It is shown that the width of the bandgap determined by the simultaneous analysis of the experimental photoelectron and inverse photoemission spectra of the surface of La₂CuO₄ using a common energy scale is underestimated by 1 eV. The electronic and satellite structures of the spectra of La₂CuO₄ are calculated on the basis of the multiband p-d model and the sudden perturbation approximation. It is shown that shakedown processes shift the one-electron contour of the final two-hole configuration of the photoelectron spectrum 1 eV down the energy scale and shift the contour of the final d¹⁰ configuration of the inverse photoemission spectrum downward by 2 eV; these shifts cause the energy splitting between the filled and empty bands to be underestimated.