Single Hole Dynamics in the ${\mathrm{CuO}}_2$ Plane at Half Filling

We present a $\mathbf{k}$-dependent study of the single hole states in ${\mathrm{Sr}}_2{\mathrm{CuO}}_2{\mathrm{Cl}}_2$. We demonstrate that the controversial “1 eV peaks” in the high $T_c$'s are quasiparticles derived from the same O $2p$ states as the Zhang-Rice (ZR) singlets, but of different symmetry and intensity in those regions of the Brillouin zone where the hybridization with the correlated Cu $3d$ states vanishes by symmetry. We use this new source of information to estimate the quasiparticle weight of the ZR singlets, discuss the quasiparticle line shape, and suggest a strong $\mathbf{k}$ dependence of the self-energy.