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Ultrafast carrier thermalization and cooling dynamics in few-layer MoS2
Zhaogang Nie1, Run Long, Linfeng Sun
1Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 637371, Singapore.
Ultrafast carrier dynamics in few-layer molybdenum disulfide (MoS2) were studied using femtosecond spectroscopy. Carrier thermalization occurs within 20 fs via carrier-carrier and carrier-phonon scattering, followed by cooling on a picosecond timescale.
Area of Science:
- Condensed matter physics
- Materials science
- Ultrafast spectroscopy
Background:
- Molybdenum disulfide (MoS2) is a 2D material with unique electronic properties.
- Understanding carrier dynamics in MoS2 is crucial for its application in optoelectronics.
Purpose of the Study:
- To investigate the ultrafast carrier dynamics in few-layer MoS2.
- To elucidate the mechanisms and timescales of carrier thermalization and cooling.
Main Methods:
- Femtosecond optical pump-probe spectroscopy with 10 fs visible pulses.
- Nonadiabatic ab initio molecular dynamics simulations.
Main Results:
- A nonthermal carrier distribution was observed immediately after photoexcitation.
- Carrier thermalization occurred within 20 fs, dependent on carrier density and temperature.
- Carrier cooling proceeded on a ~0.6 ps timescale, involving hot phonons.
- Simulations supported the experimental findings for scattering time scales.
Conclusions:
- Carrier thermalization in MoS2 involves non-Markovian quantum kinetics.
- Carrier cooling is mediated by carrier-phonon scattering and influenced by hot phonons.
- Femtosecond spectroscopy provides insights into the ultrafast carrier behavior of 2D materials.
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