Investigation of Hot Carrier Cooling Dynamics in Monolayer MoS₂

The hot carrier cooling dynamics in the C-excitonic state of monolayer MoS₂ is slowed down by the hot phonon bottleneck and Auger heating effects, as exploited by ultrafast transient absorption spectroscopy. The hot carrier cooling process, determined by the hot phonon bottleneck, can be prolonged through rising the excitation photon energy or increasing the absorbed photon flux. By inducing the Auger heating effect under higher absorbed photon flux, the hot carrier lifetime also increases at the low excitation photon energy. When these two effects are combined under higher excitation photon energy and higher absorbed photon flux, the hot phonon bottleneck is gradually weakened because of Auger recombination. In addition, the similar hot carrier phenomenon can be observed in A/B excitonic states owing to the same physical mechanism. Our work establishes a solid photophysics foundation for 2D transition-metal dichalcogenide applications in advanced energy conversion, optical quantum communication, quantum technology, etc.