Temperature dependence of the double-resonance Raman bands in bilayer - WSe2

Abstract Here, we report an analysis of the double-resonance (DR) Raman bands in bilayer tungsten diselenide (WSe2) as a function of temperature and for different laser excitation energies. Using different laser excitation energies, we verify that the double-resonance Raman is strongly enhanced in the lower laser excitation energy due to the resonance with the B exciton. Using two different laser excitation energies (1.96 eV and 2.41 eV) and changing the temperature in the range from 293 to 593 K, we determine that all mode wavenumbers decrease linearly as the temperature increases. However, the double-resonant band decay is two orders of magnitude faster than the first-order modes. This study in double-resonance Raman sheds a further insight of the excitonic state of bilayer WSe2 and shows that dispersive signature arises in terms of effects beyond the harmonic approximation, mainly electron-phonon intervalley interactions and anharmonicities.