The electronic structure of vortices in a type II superconductor is analyzed
within the quasi-classical Eilenberger framework. The possible origin of a
sixfold ``star'' shape of the local density of states, observed by scanning
tunneling microscope experiments on NbSe2​, is examined in the light of the
three effects; the anisotropic pairing, the vortex lattice, and the anisotropic
density of states at the Fermi surface. Outstanding features of split parallel
rays of this star are well explained in terms of an anisotropic s-wave
pairing. This reveals a rich internal electronic structure associated with a
vortex core.Comment: 4 pages, REVTeX, 3 figures available upon reques