d-Site Substitution Effects in the d-p Model

抄録

Effects of d-site substitution in the d-p model simulating a CuO₂-plane in high-T_c cuprates are investigated using the slave boson technique and the 1/N-expansion method. It is found that nonmagnetic impurities, e.g., Zn, substituted for Cu, strongly scatter the p-holes and drastically decrease hole densities at the neighboring O-sites. In the low doping region, the decrease reduces the Kondo temperature T_K at the neighboring Cu-sites. The repulsion U_pd between holes on the nearest neighbor Cu- and O-sites, which is known to enhance the charge susceptibility in the pure systems without impurities, turns out to promote the reduction of T_K due to the nonmagnetic impurity. Then, Cu d-spins in the vicinity of the impurity behave as local moments at temperatures higher than the reduced T_K.