Raman spectroscopy at 1550 nm. Resonant enhancement of two-phonon scattering in MoTe2 crystals

Resonance Raman scattering is widely regarded as a powerful technique for probing material properties, since it provides access not only to the vibrational spectrum but also to the interplay between electronic structure and lattice vibrations. In order to obtain such information, however, it is necessary to tune the excitation energy to match a specific electronic transition of the material under investigation. In this paper, we investigate electron-phonon interactions in bulk 2⁢H−MoTe2 near the indirect bandgap using a custom-built Raman microscope operating with an excitation laser in the infrared regime at 0.8 eV (1550 nm), a wavelength that has been rarely used in previous studies. Our experimental results, supported by ab initio calculations, demonstrate the scattering pathways responsible for the resonant enhancement of the second-order Raman peaks at 0.8 eV, while the first-order Raman scattering remains off-resonant at this excitation energy.