EFFECTS OF GAP ANISOTROPY UPON THE ELECTRONIC-STRUCTURE AROUND A SUPERCONDUCTING VORTEX

An isolated single vortex is considered within the framework of the qu asiclassical theory. The local density of states around a vortex is ca lculated in a clean type-II superconductor with an anisotropy. The ani sotropy of a superconducting energy gap is crucial for bound states ar ound a vortex. A characteristic structure of the local density of stat es, observed in the layered hexagonal superconductor 2H-NbSe2 by scann ing tunneling microscopy (STM), is well reproduced if one assumes an a nisotropic s-wave gap in the hexagonal plane. The local density of sta tes (or the bound states) around the vortex is interpreted in terms of quasiparticle trajectories to facilitate an understanding of the rich electronic structure observed in STM experiments. It is pointed out t hat further fine structures and extra peaks in the local density of st ates should be observed by STM.