Strong Exciton-Photon Interactions in the van der Waals Materials Probed by Electron Beams

Excitons in semiconducting van der Waals materials are quasi-particles with high potential applications in optoelectronics and nonlinear physics. However, their strong interaction with light and the formation of exciton-polaritons normally require the exploitation of massive photonic cavities. Here, we demonstrate strong exciton-photon interactions without the requirements for photonic cavities in Bi2Se3 and WSe2 thin films, using cathodoluminescence (CL) spectroscopy and angle-resolved CL mapping, as well as electron energy-loss spectroscopy.