The EFG Analysis of La$\\mathsf{_2}$CuO$\\mathsf{_4}$ and YBa$\\mathsf{_2}$Cu$\\mathsf{_3}$O$\\mathsf{_7}$ Based \nSuperconductors

Abstract

\nIt is shown that the 3d$_{3z^{2-r^{2}}}$ orbital of the in-plane copper and the 2p$_z$ apex oxygen orbital are absent at the Fermi level of La$_{2-x}$Sr$_x$CuO$_4$, at variance with proposals giving importance to copper-apex oxygen hybridization. At the in-plane oxygen site a sizable 2p$_z$ admixture is found at the Fermi level of YBa$_2$Cu$_3$O$_7$. The additional holes are shared among copper and oxygen sites in similar proportions. This is shown compatible with the large $U_{\\rm d}$ Emery model provided that the difference between the p and d atomic energies is comparable to the first neighbor overlap energy.\n