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In charge- or spin-ordered states, a large electric field sometimes drives the sliding motion of the ordered periodic structure. For example, CDW/SDW shows sliding motion under a large electric field[1,2]. Theoretically, the sliding motion is described as the zero energy excitation in the gapless Goldstone (phason) mode but, in reality, it is pinned by impurities and/or the commensurability, and therefore certain magnitude of electric field is needed to drive the sliding motion. The differential resistivity, which is alternating current resistivity under a DC electric field, is abruptly decreased at the threshold DC electric field. That decrease is ascribed to the onset of sliding motion. 

Here, we report a similar decrease of differential resistivity at a certain bias electric current in single-crystalline thin films of metallic helimagnet MnAu₂. This result indicates that an electric current effectively drives the sliding motion owing to the spin-transfer torque induced by the transverse component of spin moment carried from the adjacent magnetic site in the helical spin structure[3]. In the presentation, we will also show the dependences on the chirality, magnetic field, and temperature.