STM/STS observations of Pb-doped Bi-2212 single crystals

The surface states of Bi2-xPbxSr2CaCu2O8+y (Pb-Bi-2212, x=0.6) single crystals are investigated by scanning tunneling microscopy/spectroscopy in order to clarify the origin of inhomogeneous superconducting states. The topography obtained at a cleaved surface of Pb-Bi-2212 showed the coexistence of two (modulated and non-modulated) phases with domain structure of several tens of nanometers. The spatial distribution of gap amplitude observed on a modulated region showed the lack of the correlation between the gap distribution and the modulation structure. On the other hand, the weak correlation detected between the gap amplitude and bright spots on the topography obtained at 2 V bias implies the non-negligible influence of the local atomic distortion on the superconductivity