Photocarrier-phonon relaxation in highly excited monolayer transition-metal dichalcogenides

We formulate a microscopic model describing interaction between photoinjected carriers and optical phonons in monolayer transition-metal dichalcogenides which are an important example of 2D direct-bandgap semiconductors. The model takes account of the spin-valley structure of the conduction and valence bands. The evolution equations for the carrier and phonon quasi-temperatures are derived and the carrier-phonon relaxation time is estimated. We present the experimental pump-probe results for monolayer WSe2 conforming the theoretical prediction.