Low-temperature scanning tunneling microscopy and/or scanning tunneling spectroscopy measurements of heavily overdoped ${\mathrm{Bi}}_{2-x}{\mathrm{Pb}}_x{\mathrm{Sr}}_2{\mathrm{CuO}}_y$ 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 ${\mathrm{CuO}}_2$ planes. The magnitude of inhomogeneity, defined as relative standard deviation of the local gap value, is close to that of slightly overdoped ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_y$, suggesting that the electronic inhomogeneity arises from excess oxygen atoms in the ${\left(\mathrm{BiO}\right)}_2$ layers.

• Received 29 September 2005

DOI:https://doi.org/10.1103/PhysRevB.73.060502