Thermally driven ratchet motion of a skyrmion microcrystal and topological magnon Hall effect

M. Mochizuki, X. Z. Yu, S. Seki, N. Kanazawa, W. Koshibae, J. Zang, M. Mostovoy, Y. Tokura, N. Nagaosa

Research output: Contribution to journalArticle

153 Citations (Scopus)

Abstract

Spontaneously emergent chirality is an issue of fundamental importance across the natural sciences. It has been argued that a unidirectional (chiral) rotation of a mechanical ratchet is forbidden in thermal equilibrium, but becomes possible in systems out of equilibrium. Here we report our finding that a topologically nontrivial spin texture known as a skyrmion-a particle-like object in which spins point in all directions to wrap a sphere-constitutes such a ratchet. By means of Lorentz transmission electron microscopy we show that micrometre-sized crystals of skyrmions in thin films of Cu 2 OSeO 3 and MnSi exhibit a unidirectional rotation motion. Our numerical simulations based on a stochastic Landau-Lifshitz-Gilbert equation suggest that this rotation is driven solely by thermal fluctuations in the presence of a temperature gradient, whereas in thermal equilibrium it is forbidden by the Bohr-van Leeuwen theorem. We show that the rotational flow of magnons driven by the effective magnetic field of skyrmions gives rise to the skyrmion rotation, therefore suggesting that magnons can be used to control the motion of these spin textures.

Original languageEnglish
Pages (from-to)241-246
Number of pages6
JournalNature Materials
Volume13
Issue number3
DOIs
Publication statusPublished - 2014 Mar
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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  • Cite this

    Mochizuki, M., Yu, X. Z., Seki, S., Kanazawa, N., Koshibae, W., Zang, J., Mostovoy, M., Tokura, Y., & Nagaosa, N. (2014). Thermally driven ratchet motion of a skyrmion microcrystal and topological magnon Hall effect. Nature Materials, 13(3), 241-246. https://doi.org/10.1038/nmat3862