Monitoring Strain-Controlled Exciton-Phonon Coupling in Layered MoS₂ by Circularly Polarized Light

The modulation of exciton-phonon coupling by strain greatly affects the optical and optoelectronic properties of two-dimensional (2D) materials. Although photoluminescence and optical absorption spectra have been used to characterize the overall change of exciton-phonon coupling under strain, there has been no effective method to distinguish the evolution of the major contributions of exciton-phonon coupling, that is, deformation potential (DP) and Fröhlich interaction (FI). Here we report the direct monitoring of the evolution of DP and FI under strain in layered MoS₂ using circularly polarized Raman spectroscopy. We found that the relative proportions of DP and FI can be well evaluated by the circular polarization ratio of the E_2g¹ mode for strained MoS₂. Further, we demonstrated that the strain control of DP and FI in MoS₂ is dominated by the excitonic effect. Our method can be extended to other 2D semiconductors and would be helpful for manipulating exciton-phonon couplings by strain.