  Dielectric properties were investigated under various magnitudes and
directions of magnetic field (H) for a chiral magnetic insulator Cu2OSeO3. We
found that the skyrmion crystal induces electric polarization (P) along either
in-plane or out-of-plane direction of the spin vortices depending on the
applied H-direction. The observed H-dependence of P in ferrimagnetic,
helimagnetic, and skyrmion crystal state can be consistently described by the
d-p hybridization model, highlighting an important role of relativistic
spin-orbit interaction in the magnetoelectric coupling in Cu2OSeO3. Our
analysis suggests that each skyrmion particle can locally carry electric dipole
or quadrupole, which implies that the dynamics of skyrmions are controllable by
the external electric field.
