Regensburg 2025 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 10: Focus Session: Magnetic Phenomena from Phonon Chirality and Angular Momentum II (joint session MA/TT)

MA 10.4: Vortrag

Dienstag, 18. März 2025, 10:15–10:30, H16

Chiral phonons in coupled magnon-phonon band structure — •Yelyzaveta Borysenko, Daniel Schick, and Ulrich Nowak — University of Konstanz, Konstanz, Germany

Coupling of spin and lattice degrees of freedom in magnetic materials is a key aspect for angular momentum based information processing. During ultrafast demagnetization, spin angular momentum can be transferred into the lattice creating chiral phonons even in simple centrosymmetric materials [1]. Spin-lattice coupling mechanisms involved in such processes can be approached using first principles calculations, which allow to determine leading energy terms for angular momentum exchange for different materials [2, 3]. Coupled spin-lattice dynamics is then described constructing angular momentum-conserving Hamiltonian linked to ab initio calculated model parameters [4].

Here, we linearize the equations of motion and calculate coupled magnon-phonon dispersions. We discuss how different coupling terms, e.g., of anisotropy or Dzyaloshiskii-Moriya type, can modify magnon and phonon dispersions, open up energy gaps, lift the degeneracy of modes, and lead to avoided crossings in the band structure.

[1] S. R. Tauchert et al., Nature 602, 73 (2022); [2] S. Mankovsky et. al., Phys. Rev. Lett. 129, 067202 (2022); [3] J. Hellsvik et al., Phys. Rev. B 99, 104302 (2019); [4] M. Weißenhofer et al., Phys. Rev. B 108, L060404 (2023)

Keywords: spin-lattice coupling; chiral phonons; coupled excitations; avoided crossing; magnon-phonon polaron