Dresden 2026 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 40: Focus Session: Chiral phonons and crystals coupled to magnetic order II

MA 40.1: Hauptvortrag

Donnerstag, 12. März 2026, 09:30–10:00, HSZ/0002

Magnetic order induced chiral phonons in a ferromagnetic Weyl semimetal — •Luyi Yang — Tsinghua University, Beijing, China

Chiral phonons are vibrational modes in a crystal that possess a well-defined handedness or chirality, typically found in materials that lack inversion symmetry. Here we report the discovery of chiral phonon modes in the kagome ferromagnetic Weyl semimetal Co₃Sn₂S₂, a material that preserves inversion symmetry but breaks time-reversal symmetry. Using helicity-resolved magneto-Raman spectroscopy, we observe the spontaneous splitting of the doubly degenerate in-plane E_g modes into two distinct chiral phonon modes of opposite helicity when the sample is zero-field cooled below the Curie temperature, in the absence of an external magnetic field. As we sweep the out-of-plane magnetic field, this E_g phonon splitting exhibits a well-defined hysteresis loop directly correlated with the material’s magnetization. The observed spontaneous splitting reaches up to 1.27 cm⁻¹ at low temperatures, progressively diminishes with increasing temperature, and completely vanishes near the Curie temperature. Our findings highlight the role of the magnetic order in inducing chiral phonons, paving the way for novel methods to manipulate chiral phonons through magnetization and vice versa. Additionally, our work introduces new possibilities for controlling chiral Weyl fermions using chiral phonons.

Ref: [1] M. Che et al., Magnetic order induced chiral phonons in a ferromagnetic Weyl semimetal, Physical Review Letters 134, 196906 (2025).

Keywords: chiral phonon; ferromagnet; Weyl semimetal; Magneto-Raman scattering