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arXiv · 2602.16785

Magnetoelectric Raman Force on Shear Phonons in a Frustrated van der Waals Bilayer Magnet

Wolfram Brenig
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Abstract

We show that the concept of coherent phonon generation by second order response to incident electric laser fields, which is a hallmark of pump-probe spectroscopy on conventional solids, can be expanded to include frustrated quantum magnets. For that purpose, we analyze the Raman force on the shear phonons of a frustrated magnetoelectric bilayer spin system. The bilayer is a stacked triangular magnet, motivated by recently emerging type-II van der Waals multiferroic transition metal dihalides and comprises a spin system which allows for incommensurate spiral order. The magnon excitations are treated by linear spin wave theory. In the spiral state, a finite electric polarization is obtained from the spin-current interaction which induces a coupling of the magnons to the electric field. Scattering of the bilayer shear phonons from the magnons is derived from a magnetoelastic energy. In this scenario, a mixed three-point response function for the Raman force is evaluated. We find it to be strongly anisotropic and very sensitive to the magnon lifetime.

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Wolfram Brenig. 2026-02-18. Magnetoelectric Raman Force on Shear Phonons in a Frustrated van der Waals Bilayer Magnet. https://arxiv.org/abs/2602.16785

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