  In a magnetic texture, the spin of a conduction electron is forced to be
aligned to the localized moment. As a result, the topology of the magnetic
texture affects the electron dynamics in nontrivial ways. A representative
example is the topological Hall effect in noncoplanar spin textures with finite
spin chirality. While propagating in the noncoplanar spin texture, electrons
acquire Berry phase, and their motion is deflected as if they were in a
magnetic field. Here, we report a distinct Berry phase effect in a coplanar
helimagnet: the spin moment of the conduction electron is polarized under
electric currents depending on the chirality of the helimagnet. The accumulated
spin polarization works as a source of spin current, and the chirality can be
detected by the inverse spin Hall mechanism. The functionality allows us to
read out the chirality without magnetic fields, and therefore paves the way to
future helimagnet-based spintronics.
