Two-dimensional van der Waals (vdW) magnetic semiconductors CrSBr offer an ideal platform to achieve exciton-polaritons correlated with magnetic orders for developing solid-state quantum, spintronic, and photonic devices. However, for the exciton-polaritons formed by lower-energy excitons (XL = 1.37 eV), the coupling strength and nonlinear optical response are almost inert to the external magnetic field. Here, we demonstrate robust strong coupling between higher-energy excitons (XH = 1.8 eV) and photons that persists up to room temperature, along with giant magnetic-field tunability. The Rabi splitting energy is tuned up to 100 meV within a moderate 0.45 T in-plane magnetic field due to changes in excitonic states during the spin transitions. Besides, we observe significantly enhanced polariton nonlinearity in the intermediate magnetic phase, which exhibits a distinct mode-number dependence and originates from magnon-assisted long-range attractive interactions and coupling strength reduction. These results advance the development of on-demand polariton platforms for spin-correlated quantum optoelectronics.
@article{arxiv.2411.11555,
title = {Strongly Magnetically Tuned Coupling Strength and Nonlinearity in CrSBr Exciton-Polaritons},
author = {Chun Li and Chao Shen and Xuekai Ma and Kwok Kwan Tang and Nai Jiang and Xinyi Deng and Qing Wan and Jiepeng Song and Jiaqi Guo and Tian Lan and Feng Li and Yilin Wang and Xinfeng Liu and Qing Zhang},
journal= {arXiv preprint arXiv:2411.11555},
year = {2026}
}