Electronic Tunneling into an Isolated Vortex in a Clean Type II Superconductor

The electronic structure of a type II superconductor is investigated in the vicinity of an isolated vortex line by solving the Bogoliubov-de Gennes equations for the quasiparticle amplitudes. The tunneling differential conductance as a function of bias voltage is calculated at the center of the vortex; it shows a pronounced peak near zero bias originating from the lowest quasiparticle bound state. This explains recent scanning tunneling microscopy observations by Hess et al.