STAR-SHAPED LOCAL-DENSITY OF STATES AROUND VORTICES IN A TYPE-II SUPERCONDUCTOR

The electronic structure of vortices in a type II superconductor is an alyzed within the quasiclassical Eilenberger framework. The possible o rigin of a sixfold ''star'' shape of the local density of states, obse rved by scanning tunneling microscope (STM) experiments on NbSe2, is e xamined in the light of the three effects: the anisotropic pairing, th e vortex lattice, and the anisotropic density of states at the Fermi s urface. Outstanding features of split parallel rays of this star are w ell explained in terms of an anisotropic s-wave pairing. This reveals not only a rich internal electronic structure associated with a vortex core, but also unique ability of the STM spectroscopy.