Electronic structures of YBa2Cu3OY doped by La

Based on the EHMO approach, the band structures for the Y? Ba? Cu? O superconductors doped by La were calculated. The influence of the partial substitutions of La for Y and Ba in YBa₂CU₃O_y on its electronic structures was investigated. The results demonstrate that the La doping at the Ba site has a great effect on the electronic structures of the Y? Ba? Cu? O superconductors, whereas the change in the band structures caused by the La doping at the Y site is very small. The increase in the oxygen content caused by the La doping results in an increase in the densities of states at E_f, N(E_f), for La_1+x Ba_2?xCu₃O_y, but the increase in N(E_f) cannot compensate the decrease caused by the La doping at the Ba site. In addition, the 2D Cu? O planes are much more sensitive to the change in N(E_f) than are the 1D Cu? O ribbons, which implies an important role of the 2D Cu? 0 planes in the Y? Ba? Cu? O superconducting system, regardless of whether La substitutes for Y or for Ba. © 1995 John Wiley & Sons, Inc.