High-yield helicity-resolved Raman scattering with in-plane propagation of light in monolayer MoS₂

In-plane propagation of excited light in layered materials boosts the observation of novel phenomena, which differ from out-of-plane propagation. In this work, we perform the Raman study with light propagation parallel to the plane of layered MoS2. The Raman signal is unveiled at least an order of magnitude larger than that perpendicular to the plane when the excitation photon energy at ∼2.81 eV. We attribute this high-yield Raman spectra to the stronger photon-exciton coupling with in-plane propagation of light. Furthermore, we show that the exciton-mediated phonon excitation in the first-order Raman process is dominant with consideration of angular momentum transfer between phonons and photons through the measurements of the circularly polarized Raman spectra. This experimental setup configuration paves a way with high efficiency to investigate the phonon information in layered materials.