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Ultrafast carrier thermalization and cooling dynamics in few-layer MoS2

Ultrafast carrier thermalization and cooling dynamics in few-layer MoS2
Ultrafast carrier thermalization and cooling dynamics in few-layer MoS2
Femtosecond optical pump-probe spectroscopy with 10-fs visible pulses is employed to elucidate the ultrafast carrier dynamics of few-layer MoS2. A non-thermal 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 via 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 n-0.37±0.03-scaling of the thermalization time with carrier density suggests that equilibration of the non-thermal carrier distribution occurs via non-Markovian quantum kinetics. Subsequent cooling of the hot Fermi-Dirac carrier distribution occurs on the ~0.6-ps timescale via carrier-phonon scattering. Temperature- and fluence-dependence studies reveal the involvement of hot phonons in the carrier cooling process. Nonadiabatic ab initio molecular dynamics simulations, which predict carrier-carrier and carrier-phonon scattering timescales of 40 fs and 0.5 ps, respectively, lend support to the assignment of the observed carrier dynamics
1936-0851
10931-10940
Nie, Zhaogang
19d1332d-7678-4ab4-8cb6-850205e69eea
Long, Run
46fdff2a-651b-4a5a-9452-73e4c5119508
Sun, Linfeng
94cc6175-021f-4ec1-a85f-fcb26e033aa6
Huang, Chung-Che
825f7447-6d02-48f6-b95a-fa33da71f106
Zhang, Jun
fcbc4202-cc78-47ce-895e-e34b59a6dc17
Xiong, Qihua
f5abe08d-5bb7-4bd5-b9e4-cdc5b3a1093b
Hewak, Daniel W.
87c80070-c101-4f7a-914f-4cc3131e3db0
Shen, Zexiang
f17e56a3-2976-4d8c-aac0-d7e7422216ed
Prezhdo, Oleg V.
d3493782-364d-492d-b0ec-075991846a63
Loh, Zhi-Heng
a6a84562-e2c1-46d6-9b75-4874a232c52a
Nie, Zhaogang
19d1332d-7678-4ab4-8cb6-850205e69eea
Long, Run
46fdff2a-651b-4a5a-9452-73e4c5119508
Sun, Linfeng
94cc6175-021f-4ec1-a85f-fcb26e033aa6
Huang, Chung-Che
825f7447-6d02-48f6-b95a-fa33da71f106
Zhang, Jun
fcbc4202-cc78-47ce-895e-e34b59a6dc17
Xiong, Qihua
f5abe08d-5bb7-4bd5-b9e4-cdc5b3a1093b
Hewak, Daniel W.
87c80070-c101-4f7a-914f-4cc3131e3db0
Shen, Zexiang
f17e56a3-2976-4d8c-aac0-d7e7422216ed
Prezhdo, Oleg V.
d3493782-364d-492d-b0ec-075991846a63
Loh, Zhi-Heng
a6a84562-e2c1-46d6-9b75-4874a232c52a

Nie, Zhaogang, Long, Run, Sun, Linfeng, Huang, Chung-Che, Zhang, Jun, Xiong, Qihua, Hewak, Daniel W., Shen, Zexiang, Prezhdo, Oleg V. and Loh, Zhi-Heng (2014) Ultrafast carrier thermalization and cooling dynamics in few-layer MoS2. ACS Nano, 8 (10), 10931-10940. (doi:10.1021/nn504760x).

Record type: Article

Abstract

Femtosecond optical pump-probe spectroscopy with 10-fs visible pulses is employed to elucidate the ultrafast carrier dynamics of few-layer MoS2. A non-thermal 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 via 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 n-0.37±0.03-scaling of the thermalization time with carrier density suggests that equilibration of the non-thermal carrier distribution occurs via non-Markovian quantum kinetics. Subsequent cooling of the hot Fermi-Dirac carrier distribution occurs on the ~0.6-ps timescale via carrier-phonon scattering. Temperature- and fluence-dependence studies reveal the involvement of hot phonons in the carrier cooling process. Nonadiabatic ab initio molecular dynamics simulations, which predict carrier-carrier and carrier-phonon scattering timescales of 40 fs and 0.5 ps, respectively, lend support to the assignment of the observed carrier dynamics

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e-pub ahead of print date: 30 September 2014
Organisations: Optoelectronics Research Centre

Identifiers

Local EPrints ID: 370142
URI: http://eprints.soton.ac.uk/id/eprint/370142
ISSN: 1936-0851
PURE UUID: 95d5d9b8-d282-4af1-a74e-4e43e68a17ac
ORCID for Chung-Che Huang: ORCID iD orcid.org/0000-0003-3471-2463
ORCID for Daniel W. Hewak: ORCID iD orcid.org/0000-0002-2093-5773

Catalogue record

Date deposited: 23 Oct 2014 12:02
Last modified: 15 Sep 2021 01:50

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Contributors

Author: Zhaogang Nie
Author: Run Long
Author: Linfeng Sun
Author: Chung-Che Huang ORCID iD
Author: Jun Zhang
Author: Qihua Xiong
Author: Daniel W. Hewak ORCID iD
Author: Zexiang Shen
Author: Oleg V. Prezhdo
Author: Zhi-Heng Loh

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