Tunable Resonance and Electron-Phonon Coupling in Layered MoS2

TL;DR

This study investigates how resonance Raman scattering reveals phonon behavior and electron-phonon interactions in layered MoS2, especially at low frequencies and varying temperatures, highlighting anomalous phonon softening and resonance tuning.

Contribution

It provides new insights into low-frequency phonon dynamics and electron-phonon coupling in MoS2 under resonance conditions across different temperatures.

Findings

Anomalous softening of low-frequency phonon mode P3 (~34 cm-1) below 150 K.

Temperature-dependent tuning of resonance conditions affecting phonon intensities.

Evidence of electron-phonon coupling influencing phonon behavior at low temperatures.

Abstract

Resonance Raman scattering, a very effective and sensitive technique for atomically thin semiconducting transition metal dichalcogenide, can be used to observe the phonons from the entire Brillouin zone. In addition to the significance of resonance effect on the Raman spectrum it may also be used to probe the electron-phonon coupling. Our study is devoted to understand the phonons in layered MoS2, especially for very low frequency range (i.e. below 100 cm-1), as a function of temperature under the resonance effect. Understanding the phonon-phonon and electron-phonon coupling and the effects of temperature on the Raman spectrum are the central points of the present study. We observe the anomalous softening and broadening of a very low frequency phonon mode P3 (~34 cm-1) at low temperature ( i.e below 150 K). We attributed the observed anomalous trend in frequency and linewidth of this low frequency phonon to the electron-phonon coupling. Furthermore, our work also highlights the temperature induced tuning of resonance condition via understanding the intensity of phonon modes as a function of temperature.