Apical oxygens and correlation strength in electron- and hole-doped copper oxides

We use the local-density approximation in combination with the dynamical mean-field theory to carry out a comparative investigation of a typical electron-doped and a typical hole-doped copper oxide, NCCO, and LSCO, respectively. The parent compounds of both materials are strongly correlated electron systems in the vicinity of the metal to charge-transfer insulator transition. In NCCO the magnetic long-range order is essential to open a charge-transfer gap while Mott physics is responsible for the gap in LSCO. We highlight the role of the apical oxygens in determining the strength of the correlations and obtaining overall good agreement between theory and several experimentally determined quantities. Results for optical conductivity, polarized x-ray absorption, and angle-resolved photoemission are presented and compared with experiments.