Ultrafast carrier thermalization and cooling dynamics in few-layer MoS₂

Nie, Z., Long, R., Sun, L., Huang, C.C., Zhang, J., Xiong, Q., Hewak, D.W., Shen, Z., Prezhdo, O.V. and Loh, Z-H. (2015) Ultrafast carrier thermalization and cooling dynamics in few-layer MoS₂. 8th International Conference on Materials for Advanced Technologies (ICMAT 2015) [Materials Research Society of Singapore], , Singapore, Singapore. 27 Jun - 03 Jul 2015.

Abstract

Femtosecond optical pump-probe spectroscopy with 10 fs visible pulses is employed to elucidate the earliest ultrafast carrier dynamics in few-layer MoS₂. A nonthermal carrier distribution is generated immediately after the photoexcitation. Carrier thermalization is observed to occur on the <20 fs time scale via carrier and phonon scatterings. The excitation pump fluence-dependence study provides evidence for the existence of non-Markovian quantum kinetic behavior in the carrier-carrier scattering process. Subsequent cooling of the hot Fermi-Dirac carrier distribution occurs on the ~0.6 ps time scale via phonon emission on account of the observed hot-phonon effect. Nonadiabatic ab initio molecular dynamics simulations predict time constants of 30 fs and 0.5 ps, respectively, for carrier-carrier and carrier-phonon scatterings, consistent with the assignment of the observed carrier dynamics.

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Contributors

Author: C.C. Huang

Author: D.W. Hewak

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