Chiral phonons and giant magneto-optical Raman effect in chiral antiferromagnetic CoNb3S6

Chiral phonons can reverse the helicity of incident light due to their nonzero pseudo-angular momenta. In this work, we investigated chiral phonon properties in an antiferromagnetic chiral CoNb3S6 using Raman spectroscopy and theoretical calculations. We observed two doubly degenerate chiral phonons and four non-degenerate linear phonons. The chiral phonon originated from the chiral structure of Co atoms' intercalation. Giant magneto-optical Raman effect of linear A11 phonon is observed, with the rotation angle of A11 reaching up to 80° with the magnetic field changed from 0 T to 12 T. Furthermore, in contrast to ferromagnetic materials, the frequency of chiral phonons is not affected by the antiferromagnetic order. Therefore, with zero magnetization and chiral structure inherited chiral phonon, antiferromagnetic chiral materials offer special advantages for applications in magneto-optical and chiral phonon diode devices.