Local density of states in the vortex lattice in a type-II superconductor

The local density of states (LDOS) in the triangular vortex lattice is investigated based on quasiclassical Eilenberger theory. We consider the case of an isotropic s-wave superconductor with the material parameter appropriate to ${\mathrm{NbSe}}_2$. At a weak magnetic field, the spatial variation of the LDOS shows a cylindrical structure around a vortex core. On the other hand, at a high field where the core regions substantially overlap each other, the LDOS is a sixfold star-shaped structure due to the vortex lattice effect. The orientation of the star coincides with the experimental data of scanning tunneling microscopy. That is, the ray of the star extends toward the nearest-neighbor (next-nearest-neighbor) vortex direction at higher (lower) energy.