On the Mott-Hubbard Band in La2CuO4

Abstract

The Mott-Hubbard (MH) band in the charge-transfer type insulator LazCuO. is inves· tigated theoretically. The two cases in each of which either 3dx'-y' or 3daz'-r' orbit on the Cu site (with the z axis perpendicular to the CuOz plane) forms the MH-band are examined by applying Hubbard's approximation to these orbits. The relevant 2P orbits on the ligand 0 sites and a d orbit free from MH splitting are taken into account with the use of the Hartree-Fock approximation. The calculated result shows that the daz'-r' orbit can cause the MH band occupied by about one d-hole, while it is very difficult for the dx'-Y' orbit to form a MH band lying above the top valence band.