Exact diagonalization study on nonmagnetic impurity effects in high- superconductors

Tsutsui, Kenji; Toyama, Atsushi*; Toyama, Takami*; Maekawa, Sadamichi*

Substitution of impurities Zn and Ni for Cu in high- superconductors has attracted much attention. The recent neutron scattering experiment show that Ni doping traps holes in the vicinity of Ni sites. We theoretically examine the electronic state with impurity based on the model where impurity Zn and Ni 3 orbitals are explicitly treated. We carry out the numerically exact diagonalization method on small cluster. We find the region where a hole is trapped in the Ni site so that the effective hole concentration decreases and the ground state has strong antiferromagnetic correlations, as indicated from the experimental study.