Probing Temperature-Dependent Electron-Phonon and Exciton-Phonon Interactions in 2D Materials with Polarized Light

Yu-Chen Chang^1*, Yu-Chiao Chan¹, Yann-Wen Lan¹, Ting-Hua Lu¹

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

* Presenter:Yu-Chen Chang, email:yuchen9562@gapps.ntnu.edu.tw

Two-dimensional (2D) materials exhibit unique optical and electronic properties governed by strong electron-phonon and exciton-phonon interactions. In this work, we employed polarization-resolved Raman and photoluminescence spectroscopy to investigate these coupling mechanisms in MoS₂, graphene, and hBN. Under the influence of the electron-phonon coupling, we focus on the analysis of the hexagonal boron nitride, graphene, and molybdenum disulfide, especially in the presence of first-order Raman scattering to analyze the deformed electron-phonon interaction within the lattice symmetric. Meanwhile, temperature-dependent Raman measurements reveal that near-resonant excitation enhances the exciton-phonon coupling and modifies phonon symmetry. Under circularly polarized excitation, valley-polarized photoluminescence is significantly enhanced, while at low temperatures, restricted electronic transitions strengthen exciton-phonon coupling, leading to a switch in the polarization state of the Raman b mode in MoS₂. Our results highlight how polarization spectroscopy effectively probes phonon-mediated processes and offers new insight into valley dynamics for future valleytronic and quantum optoelectronic applications.

Keywords: Polarized Raman Spectroscopy, Molybdenum Disulfide, Electron-phonon coupling, Exciton-Phonon coupling, valley polarization