Coherence and Density Dynamics of Excitons in a Single-Layer MoS<sub>2</sub> Reaching the Homogeneous Limit

Jakubczyk, Tomasz; Nayak, Goutham; Scarpelli, Lorenzo; Liu, Wei-Lai; Dubey, Sudipta; Bendiab, Nedjma; Marty, Laëtitia; Taniguchi, Takashi; Watanabe, Kenji; Masia, Francesco; Nogues, Gilles; Coraux, Johann; Langbein, Wolfgang Werner; Renard, Julien; Bouchiat, Vincent; Kasprzak, Jacek

doi:10.1021/acsnano.8b09732

Cited by 38 publications

(42 citation statements)

References 57 publications

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“…Our space-, time-, and excitation/detection-frequency-resolved spectroscopy provides a unique tool to measure EXPC also in other TMDs. hBN encapsulation can lower inhomogeneous broadening of 1L-TMDs 67 , 68 , we thus expect better resolved peaks for hBN-encapsulated samples. S may be influenced by the substrate, by changing the macroscopic electric field induced by the polar LO phonon at the interface 60 .…”

Section: Resultsmentioning

confidence: 92%

Exciton–phonon coupling strength in single-layer MoSe2 at room temperature

Trovatello

Conte

et al. 2021

Nat Commun

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Single-layer transition metal dichalcogenides are at the center of an ever increasing research effort both in terms of fundamental physics and applications. Exciton–phonon coupling plays a key role in determining the (opto)electronic properties of these materials. However, the exciton–phonon coupling strength has not been measured at room temperature. Here, we use two-dimensional micro-spectroscopy to determine exciton–phonon coupling of single-layer MoSe2. We detect beating signals as a function of waiting time induced by the coupling between A excitons and A′1 optical phonons. Analysis of beating maps combined with simulations provides the exciton–phonon coupling. We get a Huang–Rhys factor ~1, larger than in most other inorganic semiconductor nanostructures. Our technique offers a unique tool to measure exciton–phonon coupling also in other heterogeneous semiconducting systems, with a spatial resolution ~260 nm, and provides design-relevant parameters for the development of optoelectronic devices.

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Section: Resultsmentioning

confidence: 92%

Exciton–phonon coupling strength in single-layer MoSe2 at room temperature

Trovatello

Conte

et al. 2021

Nat Commun

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“…By using FWM imaging, it is found that the nonlinear excited absorption of excitons and their coherent coupling can be observed at such a position ( Figure 14 a) [ 103 ]. Similar methods are also used in related research [ 105 , 106 , 107 ].…”

Section: Characterization Of 2d Materials Propertiesmentioning

confidence: 99%

Nonlinear Optical Characterization of 2D Materials

Zhou

Wang

et al. 2020

Nanomaterials

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Characterizing the physical and chemical properties of two-dimensional (2D) materials is of great significance for performance analysis and functional device applications. As a powerful characterization method, nonlinear optics (NLO) spectroscopy has been widely used in the characterization of 2D materials. Here, we summarize the research progress of NLO in 2D materials characterization. First, we introduce the principles of NLO and common detection methods. Second, we introduce the recent research progress on the NLO characterization of several important properties of 2D materials, including the number of layers, crystal orientation, crystal phase, defects, chemical specificity, strain, chemical dynamics, and ultrafast dynamics of excitons and phonons, aiming to provide a comprehensive review on laser-based characterization for exploring 2D material properties. Finally, the future development trends, challenges of advanced equipment construction, and issues of signal modulation are discussed. In particular, we also discuss the machine learning and stimulated Raman scattering (SRS) technologies which are expected to provide promising opportunities for 2D material characterization.

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“…[1][2][3][4] Such methods of ultrafast coherent spectroscopy are also employed in fundamental studies of excitons (EX), bound complexes of electrons and holes, hosted by emerging material systems and their nanostructures, such as colloidal quantum dots , 5 nanoplatelets , 6 perovskites , 7 single-layers (SLs) of semiconducting transition metal dichalcogenides 8 (TMDs) and their van der Waals heterostructures . 9 energy of several hundreds meV. With such a high binding energy -stemming from the two-dimensional confinement, reduced dielectric screening and high carrier effective masses -light-matter interaction is expected to be enhanced with respect to conventional semiconductors, like GaAs.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, an example of EX population dynamics measured via FWM was reported and discussed in Ref. [9] using MoS 2 heterostructure.…”

Section: Introductionmentioning

confidence: 99%

Coherent dynamics of resonantly excited excitons in monolayers of transition metal dichalcogenides

Jakubczyk¹,

Bartoš²,

Scarpelli³

et al. 2020

Ultrafast Phenomena and Nanophotonics XXIV

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We investigate dynamics of resonantly excited excitons in single-layers of MoSe 2 and WS 2 down to 4.5 K. To this end, we measure the delay dependence of the heterodyne four-wave mixing (FWM) amplitude induced by three, short laser pulses. This signal depends not only on the population of optically active excitons, which affects the absorption of the probe, but also on the population of optically inactive states, by interaction-induced energy shift, influencing the refractive index experienced by the probe. As such, it offers insight into density dynamics of excitons which do not directly couple to photons. Reproducing the coherent signal detected in amplitude and phase, the FWM delay dependence is modeled by a coherent superposition of several exponential decay components, with characteristic time constants from 0.1 picosecond up to 1 nanosecond. With increasing excitation intensity and/or temperature, we observe strong interference effects in the FWM field amplitude, resulting in progressively more complex and nonintuitive signal dynamics. We attribute this behaviour to increasingly populated exciton dark states, which change the FWM field phase by the relative effect on absorption and refractive index. We observe that exciton recombination occurs on a significantly longer timescale in WS 2 with respect to MoSe 2 , which is attributed to the dark character of exciton ground state in the former and the bright in the latter.

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Coherence and Density Dynamics of Excitons in a Single-Layer MoS₂ Reaching the Homogeneous Limit

Cited by 38 publications

References 57 publications

Exciton–phonon coupling strength in single-layer MoSe2 at room temperature

Exciton–phonon coupling strength in single-layer MoSe2 at room temperature

Nonlinear Optical Characterization of 2D Materials

Coherent dynamics of resonantly excited excitons in monolayers of transition metal dichalcogenides

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Coherence and Density Dynamics of Excitons in a Single-Layer MoS2 Reaching the Homogeneous Limit

Cited by 38 publications

References 57 publications

Exciton–phonon coupling strength in single-layer MoSe2 at room temperature

Exciton–phonon coupling strength in single-layer MoSe2 at room temperature

Nonlinear Optical Characterization of 2D Materials

Coherent dynamics of resonantly excited excitons in monolayers of transition metal dichalcogenides

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Coherence and Density Dynamics of Excitons in a Single-Layer MoS₂ Reaching the Homogeneous Limit