Density and symmetry of unoccupied electronic states of Tl2Ba2CaCu2O8

The local density and symmetry of unoccupied electronic states at the O and Cu sites in Tl2Ba2CaCu2O8 single crystals has been investigated by measuring O 1s and Cu 2p absorption edges. High-energy electron-energy-loss spectroscopy in transmission has been used. There are O 2px,y states at the Fermi level from the CuO2 planes and O 2pz states from the BaO and TlO layers. The empty Cu 3d states have predominantly 3dx2-y2 symmetry. There is an admixture of about 10% probably with 3d3z2-r2 character