# Raman scattering excitation spectroscopy in monolayer WS$_2$

## TL;DR

This study uses resonant Raman scattering excitation spectroscopy to explore electron-phonon interactions in monolayer WS$_2$, revealing complex excitonic effects and demonstrating the technique's potential for characterizing 2D materials.

## Contribution

It introduces the application of RSE spectroscopy to monolayer WS$_2$, uncovering detailed excitonic and phononic interactions not previously reported.

## Key findings

- Rich RSE spectra with multiple Raman features at neutral exciton resonance
- Enhanced emission from negatively charged excitons when resonant
- RSE spectroscopy effectively probes electron-phonon interactions in 2D materials

## Abstract

Resonant Raman scattering is investigated in monolayer WS$_2$ at low temperature with the aid of an unconventional spectroscopy technique, $i.e.$, Raman scattering excitation (RSE). The RSE spectrum is made up by sweeping the excitation energy, when the detection energy is fixed in resonance with excitonic transitions related to neutral and/or charged excitons. We demonstrate that the shape of the RSE spectrum strongly depends on a selected detection energy. The out-going resonance with the neutral exciton leads to an extremely rich RSE spectrum displaying several Raman scattering features not reported so far, while no clear effect on the associated background photoluminescence is observed. Instead, a strong enhancement of the emission due to the negatively charged exciton is apparent when the out-going photons resonate with this exciton. Presented results show that the RSE spectroscopy can be a useful technique to study electron-phonon interactions in thin layers of transition metal dichalcogenides.