Distribution of the Impurity Resonance Energy in Bi2Sr2CaCu2O8+δ Observed by Scanning Tunneling Spectroscopy

Using scanning tunneling microscopy and spectroscopy (STM/STS) at 4.2 K, we observed Zn impurity resonance states in single crystals of Zn substituted Bi2Sr2Ca(Cu1−x Zn x )2O8+δ . Zn impurity resonances were characterized by the peak structure in the local density of states (LDOS). The peaks were appeared near the E F on each of Zn impurity sites. The peak energy showed a wide distribution from −7 to 5 meV. The average peak energy was −1.5 meV and the variance was 1.8 meV. We investigated the correlation between the peak energy at a Zn site and the energy gap value in the region where the Zn site is embedded. Although we observed about hundred Zn sites, no correlation between the local energy gap and the peak energy was observed.