  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.
