  We have investigated vortex structures in three-dimensional superconductors
under a helical magnetic field from a chiral helimagnet numerically. In order
to obtain vortex structures, we solve three-dimensional Ginzburg-Landau
equations with the finite element method. The distribution of the helical
magnetic field is assumed to be proportional to the distribution of the
magnetic moments in the chiral helimagnet. Then, the magnetic field is the same
direction in the yz-plane and helical rotation along the helical axis. Under
this helical magnetic field, vortices appear to be perpendicular to the surface
of the superconductor. But we have found that there are tilted vortices toward
the helical axis, although there is no component of the magnetic field along
the helical axis. This vortex structure depends on the chirality of the
distribution of the helical magnetic field.
