TOWARDS MODELS OF MAGNETIC INTERACTIONS IN THE CUPRATES

摘要

The electronic structure of undoped cuprates is reanalyzed with the help of the LDA+U approach of density functional theory. It is found that in-plane oxygen orbitals forming π-bonds with copper are in energetic concurrence to those forming the Zhang-Rice singlet. The corresponding bands display a surprisingly large c-axis dispersion due to hybridization with unoccupied cation d-states in the adjacent layers. Hence, they must have relevance to c-axis magnetic coupling. In view of this situation, the Emery model is incomplete for the description of magnetism of undoped cuprates.