SKM 2021 – wissenschaftliches Programm
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SYMS: Symposium Novel phases and dynamical properties of magnetic skyrmions
SYMS 1: Novel phases and dynamical properties of magnetic skyrmions
SYMS 1.3: Hauptvortrag
Dienstag, 28. September 2021, 11:15–11:45, Audimax 2
Archimedean Screw in Driven Chiral Magnets — •Nina del Ser — Institute for Theoretial Physics, University of Cologne, Cologne, Germany
In chiral magnets a magnetic helix forms where the magnetization winds around a propagation vector q. We show theoretically that a magnetic field B⊥(t) ⊥ q, which is spatially homogeneous but oscillating in time, induces a net rotation of the texture around q. This rotation is reminiscent of the motion of an Archimedean screw and is equivalent to a translation with velocity vscrew parallel to q. Due to the coupling to a Goldstone mode, this non-linear effect arises for arbitrarily weak B⊥(t) with vscrew ∝ B⊥2 as long as pinning by disorder is absent. The effect is resonantly enhanced when internal modes of the helix are excited and the sign of vscrew can be controlled either by changing the frequency or the polarization of B⊥(t). The Archimedean screw can be used to transport spin and charge and thus the screwing motion is predicted to induce a voltage parallel to q. Using a combination of numerics and Floquet spin wave theory, we show that the helix becomes unstable upon increasing B⊥, forming a ‘time quasicrystal’ which oscillates in space and time for moderately strong drive.