Mean-field and beyond mean-field effects on the electronic structure of YBa₂Cu3O₇

The electronic structure of YBa2Cu3O7 is calculated by means of a method that operates for any self-energy approximation appropriated to strongly correlated systems. Working within the Hubbard picture, we consider mean-field and beyond mean-field approaches with two channels (p and d orbitals) for the localization. The band structure and the renormalized density of states are calculated and compared to available experimental data and theoretical results on YBa2Cu3O7. We find flat bands near the Fermi level, in agreement with angle-resolved photoemission spectra, and dispersion along kz of some bands. Our results show a multiple Hubbard splitting of the different p and d orbitals of the CuO3 chains and the CuO2 planes. This splitting leads to a redistribution of the density of holes on the oxygen sites and reasonably agrees with the characteristic disposition of bands of a charge-transfer system. © 1999 Elsevier Science B. V. All rights reserved.