Local Electronic Structure of a Single Magnetic Impurity in a Superconductor

We present the first three-dimensional, self-consistent calculation of the electronic structure near a strong classical magnetic impurity in a superconductor. Localized excited states are found within the energy gap which are half electron and half hole. The spatial structure of the positive-frequency (electronlike) spectral weight (or local density of states) can differ strongly from that of the negative frequency (holelike) spectral weight. The effect of the impurity on the continuum states above the energy gap is calculated with good spectral resolution for the first time. For sufficiently strong impurity potentials, the order parameter may change sign at the impurity site.