In the first part, I will report the discovery of chiral phonon modes in the kagome ferromagnetic Weyl semimetal C_o3S_n2S₂, 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. 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.

In the second part, I will discuss our recent findings on the magneto-optical properties of hematite (α-F_e2O₃), a candidate for altermagnetism. We have observed significant magneto-optical Kerr effect (MOKE) signals at room temperature, which are associated with the Neel vector. Furthermore, our research demonstrates that these pronounced MOKE effects facilitate optical imaging of altermagnetic domains and enable the study of their reversible domain wall motion. These findings suggest that MOKE can serve as a tool for identifying potential altermagnetic materials, potentially broadening the existing research landscape in the field of altermagnetism.

References

[1] M. Che et al., Physical Review Letters 134, 196906 (2025).

[2] J. Luo et al., Chinese Physics Letters 43, 020713 (2026).