Temperature-dependent polarized phonons in layered MoS2 under double resonance Raman scattering

Yu-Chen Chang^1*, Bipul Das¹, Yann-Wen Lan¹, Ting-Hua Lu¹

¹Department of Physics, National Taiwan Normal University, Taipei, Taiwan

* Presenter:Yu-Chen Chang, email:81041002s@gapps.ntnu.edu.tw

Polarized Raman spectroscopy can be used to observe the interactions between electron/exciton and phonons when intervalley scattering happens in two-dimensional (2D) materials. Molybdenum disulfide (MoS2) exhibits double resonance Raman scattering process when the excitation energy is close to the bandgap of the transition metal dichalcogenide (TMD) semiconductor, showing additional Raman peaks in the Raman spectrum. The electron/exciton-phonon interactions in the intervalley scattering processes are mostly determined by deformation potential (DP) and Fröhlich interaction (FI), which are not yet fully understood for the additional Raman peak of b mode observed in MoS2. In this work, we utilized linearly and circularly polarized light to investigate the polarized phonons in layered MoS2 under resonant excitation condition. A competition between the FI and DP changes the polarization of b-mode to an opposite polarization state when decreasing the temperature of measurement. These results provide an important technique to investigate light-matter interaction in 2D materials for further developments of their spintronic applications.

Keywords: Molybdenum Disulfide, Polarized Raman Spectroscopy, Helicity Exchange, Phonon, Fröhlich Interaction