Orbital polarization of the unoccupied states in multiferroic LiCu(2)O(2)

Abstract

Using measurements of polarization-dependent soft-x-ray absorption and band-structure calculations including the on-site Coulomb interaction, we investigated the symmetry of the intrinsic 3d holes in the low-dimensional quantum magnet LiCu(2)O(2) with edge-sharing spin chains. The Cu L-edge and O K-edge measurements with in-plane and out-of-plane E vectors of x ray reveal the orbital character of the valence states of Cu on different sites. The unoccupied 3d states of nominal Cu(2+) exhibit predominantly xy symmetry, whereas 3d holes of 3z(2)-r(2) symmetry reside on the nominal Cu(+) sites. Both the experimental observations and theoretical calculations agree on the hybridization of the O 2p and Cu 3d states above the Fermi level. The existence of 3d holes on Cu(+) enhances the interlayer magnetic coupling.