4 research outputs found

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

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    Band structure calculations have been used to identify the different bands contributing to the polarisation-dependent photoemission spectra of the undoped model cuprate Sr2_2CuO2_2Cl2_2 at the high-symmetry points of the CuO2_2 plane Γ\Gamma, (π/a,0)(\pi/a,0) and (π/a,π/a)(\pi/a,\pi/a) and along the high-symmetry directions Γ−(π/a,π/a)\Gamma - (\pi/a,\pi/a) and Γ−(π/a,0)\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 3dd and O 2pp orbitals 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.Comment: 13 pages, 16 figures, 5 table
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