Monitoring Strain-Controlled Exciton-Phonon Coupling in Layered MoS 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 MoS 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 mode for strained MoS. Further, we demonstrated that the strain control of DP and FI in MoS 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.