Symmetry-Dependent Exciton-Phonon Coupling in 2D and Bulk MoS2 Observed by Resonance Raman Scattering

This work describes a resonance Raman study performed on samples with one, two, and three layers (1L, 2L, 3L), and bulk MoS2, using more than 30 different laser excitation lines covering the visible range, and focusing on the intensity of the two most pronounced features of the Raman scattering spectrum of MoS2 (E-2g(1) and A(1g) bands). The Raman excitation profiles of these bands were obtained experimentally, and it is found that the A(1g) feature is enhanced when the excitation laser is in resonance with A and B excitons of MoS2, while the E-2g(1) feature is shown to be enhanced when the excitation laser is close to 2.7 eV. We show from the symmetry analysis of the exciton-phonon interaction that the mode responsible for the E-2g(1) resonance is identified as the high energy C exciton recently predicted.