Sluggish steady flow of skyrmion lattice in a confined geometry

An aggregate of magnetic skyrmions^1,2, topologically protected particlelike objects, is an emerging exotic fluid that flows under electric current^3,4. From a hydrodynamics point of view, the skyrmion fluid is peculiar in that its steady flow does not necessarily require a closed-loop skyrmion circuit. However, it remains largely unclear how this peculiarity is involved in the skyrmion steady-flow dynamics. Here, we show that the skyrmion steady flow dramatically slowdowns when the influence of system edges is not negligible. In the micrometre-sized MnSi, the steady-flow velocity is anomalously slow, as evidenced by the observation of resistance narrow-band noise with 10–10⁴ Hz, and its temperature evolution suggests that the steady flow entails thermally activated processes, which are due most likely to the skyrmion creation and annihilation at the edges. Moreover, numerical simulations reveal that the edges limit the skyrmion motion. Thus, our findings capture a vital role of the edges on the skyrmion steady flow, especially in a microstructure.

1. S. Mühlbauer, et al. Science 323, 915-919 (2009).
2. X. Z. Yu, et al. Nature 465, 901-904 (2010).
3. F. Jonietz, et al. Science 330, 1648-1651 (2010).
4. T. Schulz, et al. Nat. Phys. 8, 301-304 (2012).