SKM 2021 – scientific programme
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MA: Fachverband Magnetismus
MA 7: Skyrmions I (joint session MA/KFM)
MA 7.11: Talk
Wednesday, September 29, 2021, 12:45–13:00, H5
Solitary-waves excitations and current-induced instabilities of skyrmion strings — •Volodymyr Kravchuk1,3, Shun Okumura2, and Markus Garst1 — 1Karlsruhe Institute of Technology, Germany. — 2The University of Tokyo, Japan. — 3Bogolyubov Institute for Theoretical Physics, Kyiv, Ukraine
Field-polarized chiral magnets possess topological line excitations where the magnetization within each cross-section perpendicular to the applied field forms a skyrmion texture. We introduce and discuss an effective field-theoretical description for the low-energy dynamics of such a skyrmion string. It predicts, in particular, that skyrmion strings support solitary waves that propagate along the string while maintaining their shape. Using integrals of motion, we derive the profile of these waves analytically, and we find quantitative agreement with numerical micromagnetic simulations [1]. In addition, we discuss the influence of a spin-polarized current on the string. Whereas it is well-known that a current flowing perpendicular to the string results in a skyrmion string motion, we demonstrate that a longitudinal current destabilizes the string. This destabilization occurs via the pumping of the Goldstone mode of the string that results in a helical-shaped string deformation that increases with time. Whereas in a clean system an infinitesimal current suffices, a finite threshold current is required to destabilize the string in the presence of disorder. Moreover, we show that this current-induced instability also holds for skyrmion lattices.
[1] V. Kravchuk, U. Rößler, J. van den Brink, M. Garst, PRB, 102, 220408(R) (2020).