Chiral phonons in right- and left-handed quartzes investigated by circularly polarized Raman spectroscopy*

 Recently, chiral phonons have attracted much attention [1-5] in chiral materials. Chiral phonons have angular momentum, corresponding to lattice vibrations with rotating atomic displacements [1]. It is known that the rotation direction of the plane of linear polarization owing to optical activity is opposite in right- and left-handed chiral crystals. Analogous to optical activity, the angular momentum and propagation direction of chiral phonons are expected to be opposite in right- and left-handed chiral crystals. It was recently reported theoretically that chiral phonons belonging to certain branches of α-quartz can only propagate in either the positive or negative direction of the crystal axis [3]. Therefore, investigating chiral phonons in the chiral crystals is important for controlling their angular momentum and propagation direction. However, there are few reports of chiral phonons in crystals with different chirality. 

 We performed circularly polarized Raman spectroscopy on the right- and left-handed quartzes at room temperature. In our presentation, we will report the details of experimental results and discuss the conservation laws to be satisfied in the Raman scattering by chiral phonons.

[1] L. Zhang and Q. Niu, Phys. Rev. Lett. 112, 085503 (2014).

[2] J. Kishine et al., Phys. Rev. Lett. 125, 245302 (2020).

[3] H. Chen et al., Nano Lett. 22, 1688 (2022).

[4] E. Oishi, Y. Fujii, and A. Koreeda, arXiv: 2210.07526 (2022).

[5] K. Ishito et al., Nat. Phys. 19, 35 (2023).