Disappearance of zinc impurity resonance in large gap region on Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$ probed by scanning tunneling spectroscopy

Abstract

Using Scanning tunneling spectroscopy (STS), we report the correlation between spatial gap inhomogeneity and the zinc (Zn) impurity resonance in single crystals of Bi${}_2$Sr${}_2$Ca(Cu${}_{1-x}$Zn${}_x$)${}_2$O${}_{8+\delta }$ 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.

Phys. Rev. B Rapid Communication (Published) 4 pages, 3 figures

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