Transient photodoping and phonon dynamics in bulk and monolayer MoS2 by time resolved Raman scattering

We study the phonon dynamics of bulk and monolayer MoS2 under strong, transient photodoping by time resolved spontaneous Raman scattering (TRRS). By measuring the frequency and effective temperature evolution of each Raman active mode, TRRS allows to map the doping-induced changes in the phonon spectrum and to assess the energy transfer between the electron and phonon degrees of freedom. Our results demonstrate the occurrence of a photodoping-induced phonon renormalization and represent a first direct observation of a clear difference in the electron-phonon coupling between the “hot”, strongly coupled A-symmetry mode and the “colder” E-symmetry one. We provide a model to map the energy redistribution in bulk and monolayer MoS2, describing their different relaxation dynamics. We demonstrate that detailed information on the electronic behaviour can be drawn by probing the phonon dynamics by TRRS. That allows envisioning the tuning of electronic and transport properties of semiconducting layered materials through phononic approaches.