The hybridization of magnons (spin waves) with phonons, if sufficiently strong and comprising long-wavelength excitations, may offer a new playground when manipulating the magnetically ordered systems with light.
Applying strong magnetic fields to a van der Waals antiferromagnet, FePS3, we tune the magnon-gap excitation to coincide with the initially lower-in-energy phonon modes. Hybrid magnon-phonon modes, the magnon polarons are unveiled with the demonstration of a pronounced avoided crossing between the otherwise bare magnon and phonon excitations. The magnon polarons in FePS3 are traced with Raman scattering experiments. However, as we show, they also couple directly to terahertz photons, evoking their further explorations in the domain of antiferromagnetic opto-spintronics.
Figure – Magnetic field dependence of the energy positions of hybrid magnon-phonon modes. Full circles represent the experimental data extracted from magneto-Raman scattering measurements. This data is reproduced with solid lines, following the adequate theoretical modelling. Crosses account for the energy positions of transitions observed in FIR transmission spectra. The resonances observed in Raman scattering and FIR transmission spectra overlap within the experimental error. Dashed lines show the field dependence of energy positions of magnon modes without coupling to phonons.
Publication – Magnon-polarons in van der Waals antiferromagnet FePS3
D. Vaclavkova, M. Palit, J. Wyzula, S. Ghosh, A. Delhomme, S. Maity, P. Kapuściński, A. Ghosh, M. Veis, M. Grzeszczyk, C. Faugeras, M. Orlita, K. Sengupta, S. Datta, M. Potemski
Phys. Rev. B 104, 134437 (2021)