Theoretical analysis on chemical substitution effects of Bi-2201 superconductors

Chemical doping or substitution is most critical processes for superconductivity of cuprates. The superconductivity of Bi2Sr2CuO6+δ Bi(2201) is controlled by a partial substitution of Sr ions by Lanthanide or Bi ions. Theoretical analysis for the experimental results is presented by a quantum chemical calculation of model clusters. The suppression of superconductivity by Bi substitution occurred by the absence or the destabilization of the spin polarized anti-ferromagnetic ground state by the increase of Sr orbital contribution to the highest occupied molecular orbital (HOMO).