Oxygen hole symmetry and banding in cuprate superconductors

Abstract

A simple procedure is proposed for modeling the O 2p bands of cuprate compounds in the limit where the Cu 3d electrons are localized by correlation effects such as the on-site Coulomb energy $U_d$. This scheme, which involves orthogonalization of the linear augmented-plane-wave (LAPW) basis to the Cu 3d states, has been applied to ${\mathrm{Ca}}_{0.86}$ ${\mathrm{Sr}}_{0.14}$ ${\mathrm{CuO}}_2$, the parent compound of the Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O high-$T_c$ superconductors. Tight-binding fits to the LAPW results for ${\mathrm{Ca}}_{0.86}$ ${\mathrm{Sr}}_{0.14}$ ${\mathrm{CuO}}_2$ with localized and itinerant Cu 3d electrons yield O p-p interaction parameters which describe both limits equally well. According to this model, the doping-induced holes in the O 2p manifold depopulate initially bands containing σ-antibonding p(x,y) orbitals that are pointed along the O-Cu bond directions, with π-antibonding p(x,y) and p(z) subbands entering only at larger hole concentrations.