  Chirality is breaking of mirror symmetry in matter. In the fields of biology
and chemistry, this is particularly important because some of the essential
molecules in life such as amino acids and DNA have chirality. It is a
long-standing mystery how one of the enantiomers was chosen at the beginning
stage of life. The understanding of the emergence of homochirality under some
conditions is indispensable for the study of the origin of life as well as
pharmaceutical science. The chirality is also emergent in magnetic structures.
The longitudinal helical magnetic structure is the chiral object composed of
magnetic moments, in which the ordered direction of the magnetic moment
spatially rotates in the plane perpendicular to the propagation vector (Fig.
1a). Since the sense of rotation, which is denoted as helicity, is reversed by
any mirror operation, it is corresponding to the chirality. Here we show that
the chirality of a longitudinal helical structure can be controlled by the
magnetic field and electric current owing to the spin-transfer torque
irrelevant to the spin-orbit interaction and probed by electrical magnetochiral
effect, which is sensitive to the chiral symmetry breaking, in an itinerant
helimagnet MnP. This phenomenon is distinct from the multiferroicity in
transverse-type insulating helical magnets, in which the helical plane is
parallel to the propagation vector, because the magnetic structure has polar
symmetry not chiral one. While the combination of the magnetic field and
electric current satisfies the symmetrical rule of external stimulus for the
chirality control, the control with them was not reported for any chiral object
previously. The present result may pave a new route to the control of
chiralities originating from magnetic and atomical arrangements.
