Dependence of the energy and orbital structure of local states in CuO monolayer on Coulomb parameters

Abstract

The dependence of the energies and orbital structure of local states in the CuO monolayer on intra- and interatomic Coulomb interactions on copper and oxygen orbitals is studied. The electronic system is described within the eight-band $p-d$ model in the hole representation with the on-site energies and hopping integrals obtained using density functional theory. CuO cluster multiparticle eigenstates are calculated using exact diagonalization. The difference between the energy dependencies on the Coulomb parameters for the states with the predominant probability density on the $d$-orbital and the states in which hole occupies $p$-orbitals leads to crossover of $d$- and $p$-states. The ground single-hole and two-hole states which determine the electronic structure of the low-energy excitations have the character of $d$- or $p$-orbitals in the different regions of the Coulomb parameters space. The gap between the energies of the dispersionless quasiparticles forming the top of the valence band and conductivity band also have different values in these two regions. The magnitude of this gap and the orbital character of the local multiparticle states change sharply even with an insignificant change in the Coulomb interactions within the boundary region of parameters between the regions in which the local states are formed by the $d$- or $p$-orbitals.