On-line SPICE-SPIN+X Seminars

On-line Seminar: 20.10.2021 - 15:00 German Time

Archimedean screw and time quasi-crystals in driven chiral magnets

Achim Rosch, Institute for Theoretical Physics, University of Cologne

The Archimedean screw is one of the oldest machines of mankind. We show theoretically [1] how one can realize and drive such an Archimedean screw
in chiral magnets, where helical spin textures are realized. A small oscillating magnetic field at GHz frequencies induces a net rotation and screw-like motion of the magnetic texture. This effect arises from the coupling of the oscillating field to the Goldstone mode of the system. The Archimedean screw can be used to transport spin and charge and thus the screwing motion is predicted to induce a large voltage in metallic systems. Using a combination of numerics and Floquet spin wave theory, we show that the helix becomes unstable upon increasing the oscillating field forming a `time quasicrystal' which oscillates in space and time for moderately strong drive.

[1] Nina del Ser, Lukas Heinen, Achim Rosch, SciPost Phys. 11, 009 (2021).

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