Atomic-scale studies of impurities in superconductors with a scanning tunneling microscope

Imaging and spectroscopy with a cryogenic scanning tunneling microscope (STM) have been used to study the local variation of electronic states on the atomic scale in both low-Tc and high-Tc superconductors. These experiments provide an atomic-scale perspective of impurity scattering by directly probing the localized excitations that are induced by individual impurities.