Nonlocal Effect of Local Nonmagnetic Impurity in High-Tc   Superconductors: Induced Local Moment and Huge Residual Resistivity
  We study a Hubbard model with a strong onsite impurity potential based on an improved fluctuation-exchange (FLEX) approximation, which we call the GVI-FLEX method. We find that (i) both local and staggered susceptibilities are strongly enhanced around the impurity. By this reason, (ii) the quasiparticle lifetime as well as the local density of states (DOS) are strongly suppressed in a wide area around the impurity (like a Swiss cheese hole), which causes the ``huge residual resistivity'' beyond the s-wave unitary scattering value. These results by the GVI method naturally explains the various impurity effects in HTSC's in a unified way, which had been a long-standing theoretical problem. 
Hiroshi Kontani, Masanori Ohno