Ab Initio determination of Cu 3d orbital energies in layered copper oxides

Abstract

It has long been argued that the minimal model to describe the low-energy physics of the high T c superconducting cuprates must include copper states of other symmetries besides the canonical 3d x2-y2one, in particular 3d 2x the orbital. Experimental and theoretical estimates of the energy splitting of these states vary widely. With a novel ab initio quantum chemical computational scheme we determine these energies for a range of copper-oxides and-oxychlorides, determine trends with the apical Cu-ligand distances and find excellent agreement with recent Resonant Inelastic X-ray Scattering measurements, available for La 2 CuO 4, Sr 2 CuO 2 Cl 2, and CaCuO 2.