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Transient SHG Imaging on Ultrafast Carrier Dynamics of MoS2 Nanosheets

Transient SHG Imaging on Ultrafast Carrier Dynamics of MoS2 Nanosheets
Jang, H.Dhakal, K.P.Joo, K.-I.Yun, Won SeokShinde, S.M.Chen, X.Jeong, Soon MoonLee, S.W.Lee, Z.Lee, Jae DongAhn, J.-H.Kim, Hyun Min
DGIST Authors
Jeong, Soon MoonLee, Jae DongKim, Hyun Min
Issue Date
Advanced Materials, 30(14), 1705190
Article Type
Author Keywords
Photoinduced acoustic phononsTransient second-harmonic generation microscopyUltrafast carrier dynamicsExcitonsMolybdenum disulfide
Understanding the collaborative behaviors of the excitons and phonons that result from light-matter interactions is important for interpreting and optimizing the underlying fundamental physics at work in devices made from atomically thin materials. In this study, the generation of exciton-coupled phonon vibration from molybdenum disulfide (MoS2) nanosheets in a pre-excitonic resonance condition is reported. A strong rise-to-decay profile for the transient second-harmonic generation (TSHG) of the probe pulse is achieved by applying substantial (20%) beam polarization normal to the nanosheet plane, and tuning the wavelength of the pump beam to the absorption of the A-exciton. The time-dependent TSHG signals clearly exhibit acoustic phonon generation at vibration modes below 10 cm-1 (close to the Γ point) after the photoinduced energy is transferred from exciton to phonon in a nonradiative fashion. Interestingly, by observing the TSHG signal oscillation period from MoS2 samples of varying thicknesses, the speed of the supersonic waves generated in the out-of-plane direction (Mach 8.6) is generated. Additionally, TSHG microscopy reveals critical information about the phase and amplitude of the acoustic phonons from different edge chiralities (armchair and zigzag) of the MoS2 monolayers. This suggests that the technique could be used more broadly to study ultrafast physics and chemistry in low-dimensional materials and their hybrids with ultrahigh fidelity. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Wiley-VCH Verlag
Related Researcher
  • Author Lee, JaeDong Light and Matter Theory Laboratory
  • Research Interests Theoretical Condensed Matter Physics; Ultrafast Dynamics and Optics; Nonequilibrium Phenomena
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Division of Energy Technology1. Journal Articles
Department of Emerging Materials ScienceLight and Matter Theory Laboratory1. Journal Articles
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