Resonance effects in the Raman scattering of mono- and few layers MoSe$_2$

TL;DR

This study investigates how resonant Raman scattering spectra of mono- and multilayer MoSe₂ are influenced by exciton-phonon interactions, revealing resonance behaviors linked to different excitonic states and phonon symmetries.

Contribution

It provides a detailed analysis of resonance effects in Raman spectra of MoSe₂, highlighting symmetry-dependent exciton-phonon coupling and resonance behaviors of specific phonon modes.

Findings

Resonance enhancement of high-energy phonons near C exciton energy.

Symmetry-dependent exciton-phonon coupling affects low-energy phonon modes.

Resonance of shear and breathing modes with specific electronic excitations.

Abstract

Using resonant Raman scattering spectroscopy with 25 different laser lines, we describe the Raman scattering spectra of mono- and multi-layers 2H-molybdenum diselenide (MoSe$_2$) as well as the different resonances affecting the most pronounced features. For high-energy phonons, both A- and E- symmetry type phonons present resonances with A and B excitons of MoSe$_2$ together with a marked increase of intensity when exciting at higher energy, close to the C exciton energy. We observe symmetry dependent exciton-phonon coupling affecting mainly the low-energy rigid layer phonon modes. The shear mode for multilayer displays a pronounced resonance with the C exciton while the breathing mode has an intensity that grows with the excitation laser energy, indicating a resonance with electronic excitations at energies higher than that of the C exciton.