Electronic inhomogeneity of heavily overdoped Bi2-x Pbx Sr2 CuOy studied by low-temperature scanning tunneling microscopy/spectroscopy

Low-temperature scanning tunneling microscopy and/or scanning tunneling spectroscopy measurements of heavily overdoped Bi2-x Pbx Sr2 CuOy have revealed nanoscale electronic inhomogeneity composed of spatial regions showing superconducting and pseudogaplike gap structures. This proves that the inhomogeneity is a general feature of Bi-based cuprates, regardless of the number of CuO2 planes. The magnitude of inhomogeneity, defined as relative standard deviation of the local gap value, is close to that of slightly overdoped Bi2 Sr2 CaCu2 Oy, suggesting that the electronic inhomogeneity arises from excess oxygen atoms in the (BiO)2 layers.