ROLE OF CU 4S-BAND IN CU 2P-XPS OF ND2-XCEXCUO4

The role of the Cu 4s band in the Cu 2p-XPS of Nd2-xCexCuO4 is investigated on the basis of the impurity Anderson model. The model consists of the impurity Cu 3d shell and the conduction and valence bands formed from the O 2p and Cu 4s bands under the tight-binding approximation. Because of the symmetry of the crystal, the 3d states couple weakly to the Cu 4s band so that the effect of the 4s band on the Cu 2/7-XPS is very small in general. However, in the case where the 4s band is lower by a few eV in energy than that estimated by the first-principle calculation, the 4s state is important in the electron doping process in Nd2-xCexCuO4 because the doped electron enters this state. © 1990, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.