The recent discovery of 2D magnets has revealed various intriguing phenomena due to the coupling between spin and other degree of freedoms (such as helical photoluminescence, nonreciprocal SHG). Previous research on the spin-phonon coupling effect mainly focuses on the renormalization of phonon frequency. Here we demonstrate that the Raman polarization selection rules of optical phonons can be greatly modified by the magnetic ordering in 2D magnet CrI3. For monolayer samples, the dominant A1g peak shows abnormally high intensity in the cross polarization channel at low temperature, which is forbidden by the selection rule based on the lattice symmetry. While for bilayer, this peak is absent in the cross polarization channel for the layered antiferromagnetic (AFM) state and reappears when it is tuned to the ferromagnetic (FM) state by an external magnetic field. Our findings shed light on exploring the emergent magneto-optical effects in 2D magnets.
@article{arxiv.1910.04542,
title = {Magnetic order induced polarization anomaly of Raman scattering in 2D magnet CrI$_3$},
author = {Yujun Zhang and Xiaohua Wu and BingBing Lv and Minghui Wu and Shixuan Zhao and Junyang Chen and Mengyuan Jia and Chusheng Zhang and Le Wang and Xinwei Wang and Yuanzhen Chen and Jiawei Mei and Takashi Taniguchi and Kenji Watanabe and Hugen Yan and Qihang Liu and Li Huang and Yue Zhao and Mingyuan Huang},
journal= {arXiv preprint arXiv:1910.04542},
year = {2020}
}