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MA: Fachverband Magnetismus

MA 37: Skyrmions III

MA 37.8: Vortrag

Donnerstag, 21. März 2024, 11:30–11:45, EB 301

Nonlinear dynamics and stability of skyrmion strings — •Volodymyr Kravchuk — Leibniz Institute for Solid State and Materials Research, , Helmholtzstraße 20, 01069 Dresden

Here we analyze the nonlinear dynamics of a skyrmion string in a low-energy regime by means of the collective variables approach. Using the perturbative method of multiple scales (both in space and time), we show that the weakly nonlinear dynamics of the translational mode propagating along the string is captured by the focusing-type nonlinear Schroedinger equation [1]. As a result, the basic planar-wave solution, which has the form of a helix-shaped wave, experiences modulational instability. The latter leads to the formation of cnoidal waves. Both types of cnoidal waves, dn- and cn-waves, as well as the separatrix soliton solution, are confirmed by micromagnetic simulations. Beyond the class of traveling-wave solutions, we found Ma-breather propagating along the string. Finally, we proposed a generalized approach that enables one to describe the nonlinear dynamics of the modes of different symmetries, e.g., radially symmetrical or elliptical.

By computing the spectrum of the magnons propagating along the string in the presence of the longitudinal spin current, we found the current-induced Goldstone spin wave instability. A longitudinal current is thus able to melt the skyrmion string lattice via a nonequilibrium phase transition [2].

[1] V.P. Kravchuk, Phys. Rev. B 108, 144412 (2023).

[2] S. Okumura, V.P. Kravchuk, M. Garst, Phys. Rev. Lett. 131, 066702 (2023).

Keywords: Skyrmion string; Nonlinear Schroedinger equation; Spin polarized current