10.1021/nn504760x.s001 Zhaogang Nie Zhaogang Nie Run Long Run Long Linfeng Sun Linfeng Sun Chung-Che Huang Chung-Che Huang Jun Zhang Jun Zhang Qihua Xiong Qihua Xiong Daniel W. Hewak Daniel W. Hewak Zexiang Shen Zexiang Shen Oleg V. Prezhdo Oleg V. Prezhdo Zhi-Heng Loh Zhi-Heng Loh Ultrafast Carrier Thermalization and Cooling Dynamics in Few-Layer MoS<sub>2</sub> American Chemical Society 2014 carrier density Ultrafast Carrier Thermalization carrier cooling process broadband laser pulse Nonadiabatic ab initio ultrafast carrier dynamics nonthermal carrier distribution thermalization time B excitonic transitions 2014-10-28 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Ultrafast_Carrier_Thermalization_and_Cooling_Dynamics_in_Few_Layer_MoS_sub_2_sub_/2241463 Femtosecond optical pump–probe spectroscopy with 10 fs visible pulses is employed to elucidate the ultrafast carrier dynamics of few-layer MoS<sub>2</sub>. A nonthermal carrier distribution is observed immediately following the photoexcitation of the A and B excitonic transitions by the ultrashort, broadband laser pulse. Carrier thermalization occurs within 20 fs and proceeds <i>via</i> both carrier–carrier and carrier–phonon scattering, as evidenced by the observed dependence of the thermalization time on the carrier density and the sample temperature. The <i>n</i><sup>–0.37±0.03</sup> scaling of the thermalization time with carrier density suggests that equilibration of the nonthermal carrier distribution occurs <i>via</i> non-Markovian quantum kinetics. Subsequent cooling of the hot Fermi–Dirac carrier distribution occurs on the ∼0.6 ps time scale <i>via</i> carrier–phonon scattering. Temperature- and fluence-dependence studies reveal the involvement of hot phonons in the carrier cooling process. Nonadiabatic <i>ab initio</i> molecular dynamics simulations, which predict carrier–carrier and carrier–phonon scattering time scales of 40 fs and 0.5 ps, respectively, lend support to the assignment of the observed carrier dynamics.