Quantum interference of a Zn impurity in d -wave superconductors

The local differential tunneling conductance on a Zn impurity in a disordered d -wave superconductor is studied. Quantum interference between many impurities leads to definitive quasiparticle spectra. We suggest that an elaborate analysis on impurity-induced spectra with quantum interference effects included may be able to pin down the sign and strength of the scattering potential of a Zn impurity in the low-density limit. Numerical simulations calculated with appropriately determined impurity parameters are in satisfactory agreement with the observations from scanning tunneling microscopy experiments even in subtle details.