Local Electronic Structure of Defects in Superconductors

Abstract

Publisher Summary The local electronic structure around a defect reflects both the properties of a defect and the medium in which it is embedded. For a strong nonmagnetic or magnetic impurity in a superconductor, the distortion of the normal-state properties by the strong impurity plays a vital role in the response of the superconducting medium. The chapter discusses that in the case of a nonmagnetic impurity with no localized states around it, the local density of states (LDOS) for the inhomogeneous superconductor is merely the normalized LDOS for the inhomogeneous normal metal multiplied by the homogeneous superconductor's density of states. This suggests some caution regarding the method used to normalize STM spectra taken at different places on a superconductor's surface. For an impurity embedded in a host with an anisotropic order parameter, the anisotropy of the host produces rich spatial structure in the LDOS around the impurity. The self-consistent calculations have been performed with a new, powerful Koster–Slater technique that allows the Gor’kov equation to be solved in principle. It is well suited for scanning tunneling microscopy (STM) probes of condensed electronic systems, for its strength is in determining the short-length scale, low-energy properties of the system. .