Analysis of the valence-band photoemission spectrum of Sr2CuO2Cl2 along the high-symmetry directions

Band structure calculations have been used to identify the different bands contributing to the polarization-dependent photoemission spectra of the undoped model cuprate Sr2CuO2Cl2 at the high-symmetry points of the CuO2 plane Gamma, (pi,/a,0) and (pi/a, pi/a) and along the high-symmetry directions Gamma-(pi/a, pi/a) and Gamma - ( pi/a, 0). Results from calculations within the local density approximation (LDA) have been compared with calculations taking into account the strong electron correlations by LDA+U, with the result that the experimental order of energy levels at the high-symmetry points is better described by the LDA+U calculation than by the simple LDA. All the main peaks in the photoemission spectra at the high symmetry points could be assigned to different Cu 3d and O 2p orbitalis which we have classified according to their point symmetries. The dispersions along the high-symmetry directions were compared with an 11-band tight-binding model which was fitted both to the LDA+U band structure calculation and the angle-resolved photoemission data. The mean field treatment successfully describes the oxygen derived bands but shows discrepancies for the copper ones. [S0163-1829(99)01925-6].