Yue Meng Qualifier

Two-dimensional van der Waals (vdW) magnetic materials host low-dimensional magnetism together with a rich variety of collective excitations. The coupling among lattice, spin, and charge degrees of freedom is of significant interest, and excitonic coupling plays an important role in mediating and probing these interactions. Excitons can serve as an optical interface to access otherwise hidden degrees of freedom and can also hybridize with other coherent excitations to form novel collective modes.

In this presentation, we show how coherent terahertz excitation combined with time-resolved optical spectroscopy can reveal these coupling mechanisms. We present experiments on the multiferroic NiI₂, demonstrating coupling between electromagnons and excitons, as well as excitonic sensitivity to chirality encoded in opposite multiferroic domains. We also explore the possibility of realizing a phonoriton, a hybrid excitation involving excitons, photons, and phonons, in the van der Waals magnet CrSBr.