Emergent electrodynamics of skyrmions in a chiral magnet

By T. Schulz, R. Ritz, A. Bauer, M. Halder, M. Wagner, C. Franz, C. Pfleiderer, K. Everschor, M. Garst, Achim Rosch. Nature Physics, 2012

863 citations recorded by the source corpus.

An experiment demonstrates that the motion of so-called skyrmions—topologically quantized magnetic whirls—causes an emergent electric field that inherits the topological quantization of the skyrmions and is directly visible in the Hall effect. When an electron moves in a smoothly varying non-collinear magnetic structure, its spin orientation adapts constantly, thereby inducing forces that act both on the magnetic structure and on the electron. These forces may be described by electric and magnetic fields of an emergent electrodynamics1,2,3,4. The topologically quantized winding number of so-called skyrmions—a type of magnetic whirl discovered recently in chiral magnets5,6,7—has been predicted to induce exactly one quantum of emergent magnetic flux per skyrmion. A moving skyrmion is therefore expected to induce an emergent electric field following Faraday’s law of induction, which inherits this topological quantization8. Here we report Hall-effect measurements that establish quantitatively the predicted emergent electrodynamics. We obtain quantitative evidence for the depinning of skyrmions from impurities (at current densities of only 106 A m−2) and their subsequent motion. The combination of exceptionally small current densities and simple transport measurements offers fundamental insights into the connection between the emergent and real electrodynamics of skyrmions in chiral magnets, and might, in the long term, be important for applications.

Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics

View Paper: https://www.semanticscholar.org/paper/aae02f536d4e5904f09835bb6241f4ab2722bf0b

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Citations in the corpus

Heusler 4.0: Tunable Materials (2016, background): “The domain wall can be replaced by other non-collinear spin textures such as skyrmions (72).”
Current-induced skyrmion dynamics in constricted geometries. (2013, background): “This characteristic can be explained by the Thiele equation for the centre of mass R = (X, Y ) [14, 15] of a spin texture (see Supplementary Information I for details):”
Interface-Induced Phenomena in Magnetism (2016, neutral): “In these materials, electrons moving in an electric-field experience an effective magnetic field that couples to their magnetic moment due to spin-orbit coupling, leading to emergent electrodynamic phenomena such as the topological Hall effect and the nonlinear (the Hall voltage depends nonlinearly ”
Fluctuation-induced first-order phase transition in Dzyaloshinskii-Moriya helimagnets (2012, background): “Moreover, in the skyrmion phase of MnSi spin transfer torques have been observed at record low current densities j = 10(6) A m−2 making these materials interesting for spintronic applications [25, 26].”
Spin insulatronics (2020, background): “Importantly, we can manipulate these topologically robust nanoscale spin textures with low current density [55, 56, 57, 58, 59].”
Magnetic texture based magnonics (2020, background): “Skyrmions can be formed by DMI, and have been observed in intrinsic chiral magnets [60, 38, 366, 367, 368, 155] with bulk DMI and magnetic multilayers [369, 370] with interfacial DMI.”