Disappearance of zinc impurity resonance in large gap region on Bi$_{mathrm{2}}$Sr$_{mathrm{2}}$CaCu$_{mathrm{2}}$O$_{mathrm{8+}delta}$ probed by scanning tunneling spectroscopy

Using Scanning tunneling spectroscopy (STS), we report the correlation between spatial gap inhomogeneity and the zinc (Zn) impurity resonance in single crystals of Bi$_{mathrm{2}}$Sr$_{mathrm{2}}$Ca(Cu$_{mathrm{1-}x}$Zn$_{x}$)$_{mathrm{2}}$O$_{mathrm{8+}delta}$ with different carrier (hole) concentrations ($p$) at a fixed Zn concentration ($x$ $sim$ 0.5 % per Cu atom). In all the samples, the impurity resonance lies only in the region where the gap value is less than $sim$ 60 meV. Also the number of Zn resonance sites drastically decreases with decreasing $p$, in spite of the fixed $x$. These experimental results lead us to a conclusion that the Zn impurity resonance does not appear in the large gap region although the Zn impurity evidently resides in this region.