Electronic Structure of Impurities and Vortices in Short Coherence Length Superconductors

摘要

This is a final report on theoretical calculation of scanning tunneling microscopy spectra near impurities in superconductors. Calculations have been performed for superconductors with isotropic and anisotropic gaps using a newly developed Green's function technique. This technique provides essentially arbitrary energy resolution and is applicable to strong or weak- coupling superconductors with long or short coherence lengths and arbitrary energy gaps. An analytic model has been developed for impurities in superconductors with either anisotropic or isotropic gaps. Calculation of planar tunneling spectra can reproduce the (quite different) results from several different groups with a d-wave gap and a small amount (1%) of impurities. These impurities are believed to be oxygen vacancies. A systematic investigation of the properties of impurity-associated resonance states in the gap has also been done.