Self-Hybridized Polaritons in a Van der Waals Magnet

Recent discoveries of van der Waals magnetic materials have opened up new possibilities for exploring magnetic order in reduced dimensions, with implications for quantum phenomena and device applications. Among these materials, CrSBr stands out as a promising candidate. It consists of monolayer ferromagnets stacked into an A-type antiferromagnetic structure and exhibits a high Neel temperature. Furthermore, as a semiconductor with strong coupling between excitons and magnetism, CrSBr provides a novel platform for optical manipulation of its magnetic properties. With tightly-bound excitons and large oscillator strength, CrSBr supports strong light-matter coupling, leading to the formation of polaritons—hybrid quasi-particles formed by the coupling of excitons and photons. Our study focuses on self-hybridized polaritons in CrSBr samples, capitalizing on the material's high refractive index to achieve strong light confinement without external mirrors. In particular, we utilize polarization-resolved photoluminescence excitation (PLE) spectroscopy to comprehensively investigate the anisotropic properties of CrSBr. Our work sheds light on the light-matter coupling in CrSBr, offering insights for optically accessible device applications in spintronics and magnonics.