Crucially, the magnon symmetry differs depending on the magnetic ground state and the space group symmetries. A large class of vdWs magnets crystallizes with a honeycomb spin lattice, where the magnetic order ranges from simple patterns such as ferromagnetic and Néel-type order to the more complex orders of stripe and zigzag AFM 34. Recently discovered van der Waals (vdWs) magnets 20, 21, 22, 23, 24, 25 exhibit strong spin-lattice interactions and possess unprecedented tunability via pressure 26, strain 27, electrostatic gating 28, 29, 30, and moiré engineering 31, 32, 33, thereby offering an ideal platform to explore chiral spin-lattice excitations in the 2D limit. However, the strong coupling of magnons and chiral phonons remains elusive, also the details and prerequisites of chiral phonon formation in a magnetic system are largely unclear. Experimentally, the characteristic avoided crossing between the magnon and phonon bands has been observed in both 3D 10, 11, 12, 13 and layered magnets 14, 15, 16, 17, 18, 19 indicating the strong coupling and the formation of the hybrid quasiparticles, magnon polarons (MP). The strong coupling between magnons and chiral phonons is expected to offer a coherent path for energy and angular momentum transfer between the two degrees of freedom, and form a hybrid spin-lattice excitation with chirality.Īs a dynamical form of coherent spin-lattice interactions, the magnon-phonon strong coupling has received great theoretical attention 4, 5, 6, 7, 8, 9, where coupling-induced topological magnons have been predicted for 2D magnetic systems 6, 7, 8, 9. Collective spin and lattice excitations with finite angular momenta, e.g., magnons and chiral phonons, are of particular importance in processes related to angular momentum transfer and conservation, e.g., in spintronics and ultrafast magnetism 3. Strongly coupled spin and lattice degrees of freedom play essential roles in diverse quantum materials phenomena, from driving multiferroic polarization to manipulating magnetic order via lattice vibrations 1, 2. The observation of coherent chiral spin-lattice excitations at zero magnetic field paves the way for angular momentum-based hybrid phononic and magnonic devices. This coupling lifts the chiral phonon degeneracy and gives rise to an unusual Raman circular polarization of the chiMP branches. Via first principle calculations, we uncover a coherent coupling between AFM magnons and chiral phonons with parallel angular momenta, which arises from the underlying phonon and space group symmetries. The hybridization gap reaches 0.25 meV and survives down to the quadrilayer limit. With a combination of magneto-infrared and magneto-Raman spectroscopy, we observe chiral magnon polarons (chiMP), the new hybridized quasiparticles, at zero magnetic field. Here, we report the observation of magnon-induced chiral phonons and chirality selective magnon-phonon hybridization in a layered zigzag antiferromagnet (AFM) FePSe 3. However, the interplay between magnons and chiral phonons as well as the details of chiral phonon formation in a magnetic system are yet to be explored. Recent advances show angular momentum can also be carried by lattice vibrations in the form of chiral phonons. Two-dimensional (2D) magnetic systems possess versatile magnetic order and can host tunable magnons carrying spin angular momenta.
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