Excitonic properties of semiconducting monolayer and bilayer 
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Robert, Cédric; Picard, Raphaël; Lagarde, Delphine; Wang, G; Echeverry, J. P.; Cadiz, Fabian; Renucci, Pierre; Högele, Alexander; Amand, T.; Marie, X.; Gerber, Iann C.; Urbaszek, B.

doi:10.1103/physrevb.94.155425

Cited by 74 publications

(83 citation statements)

References 76 publications

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“…We also noticed in Fig.1 (c) that the emission for hole-trions (T + ) for the bilayer sample is much stronger than that for electron-trions (T -). The PL spectra show predominantly two peaks centered at 1.137 eV and 1.124 eV, labeled as X2 and T -, which correspond to exciton and trion for bilayer MoTe2, respectively, consistent with previous observations (19,(34)(35)(36)(37). Figure 2 (b) shows a series of differential reflectance spectra with increasing excitation as processed using equation (1).…”

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confidence: 87%

Excitonic complexes and optical gain in two-dimensional molybdenum ditelluride well below the Mott transition

et al. 2020

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†These authors contributed equally to this work. AbstractStrong Coulomb interaction in 2D materials provides unprecedented opportunities for studying many key issues of condensed matter physics, such as co-existence and mutual conversions of excitonic complexes, fundamental optical processes associated with their conversions, and their roles in the celebrated Mott transition. Recent lasing demonstrations in 2D materials raise important questions about the existence and origin of optical gain and possible roles of excitonic complexes. While lasing occurred at extremely low densities dominated by various excitonic complexes, optical gain was observed in the only experiment at densities several orders of magnitude higher, exceeding the Mott density. Here, we report a new gain mechanism involving charged excitons or trions well below the Mott density in 2D molybdenum ditelluride. Our combined experimental and modeling study not only reveals the complex interplays of excitonic complexes well below the Mott transition, but also provides foundation for lasing at extremely low excitation levels, important for future energy efficient photonic devices.Dynamical processes of quasiparticles such as excitons and their various associated complexes (including charged excitons or trions, bi-excitons, and other highly correlated objects (1)) in solids are at the very core of fundamental condensed matter physics. The evolution of physical states from low to high carrier density involves (2-5) the insulating exciton gas, Bose-Einstein condensate (BEC) (2), co-existence of various excitonic complexes, crossover or transitions to conducting electron-hole plasmas (EHP), or electron-hole liquid (EHL) (3) through the Mott transition (MT) (4). There remain many fundamental issues to be understood associated with the evolution of such quantum quasiparticles and the related phase transitions, especially in the intermediate density regime involving highly correlated complexes. On the other hand, mutual conversions of these excitonic complexes and related phase transitions are also profoundly linked to the natures of different optical processes in semiconductors as carrier density increases (5,6). Light-semiconductor interaction thus plays important dual roles: As an information reporter, the interaction reveals the intrinsic dynamics of evolution, co-existence, and mutual conversion of various excitonic complexes in their passage towards degenerate EHP or EHL through MT, providing deep understandings of physical processes when carrier density is successively increased. At the same time, different conversion processes among various excitonic complexes provide novel absorption or emission mechanisms, forming the physical foundations for photonic functionalities including lasers, solar cells, light emitting diodes, and many other devices. While optical processes are well-understood in the two extremes: pure exciton gas and highly degenerate EHP, the intermediate stages involving various excitonic complexes are much less understood. Recent stud...

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confidence: 87%

Excitonic complexes and optical gain in two-dimensional molybdenum ditelluride well below the Mott transition

et al. 2020

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“…Planar photonic crystals can integrate the 2D materials to form hybrid systems of different functionality [12]. We are interested in materials with optical gap, which have exciton resonance with strong oscillator strength, like TMDs [13,14]. These * kazanovdr@gmail.com 2D semiconductors possess unique properties that differs from those in their 3D analogues [15].…”

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Resonant photonic crystals based on van der Waals heterostructures for effective light pulse retardation

Kazanov

Poshakinskiy

Shubina

2017

Superlattices and Microstructures

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“…This allows working towards devices based on bias controlled phase changes in monolayer MoTe 2 [47,48]. First studies of 2H−MoTe 2 flakes exfoliated on SiO 2 have identified monolayers as direct semiconductors [49,50], interestingly the nature of the gap of the bilayer is still under discussion [51,52]. So in practice the difference between mono-and bilayers has to be confirmed in Raman experiments, see Fig.…”

Section: Excited State Spectroscopy In ML Mote2mentioning

confidence: 99%

“…Data from DFT calculations summarized in Ref [59]. for S and Se-based MLs and from Ref [51]. for MoTe2 MLs.…”

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Exciton States in Monolayer MoSe2 and MoTe2 Probed by Upconversion Spectroscopy

et al. 2018

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Transitions metal dichalcogenides (TMDs) are direct semiconductors in the atomic monolayer (ML) limit with fascinating optical and spin-valley properties. The strong optical absorption of up to 20 % for a single ML is governed by excitons, electron-hole pairs bound by Coulomb attraction. Excited exciton states in MoSe2 and MoTe2 monolayers have so far been elusive due to their low oscillator strength and strong inhomogeneous broadening. Here we show that encapsulation in hexagonal boron nitride results in emission line width of the A:1s exciton below 1.5 meV and 3 meV in our MoSe2 and MoTe2 monolayer samples, respectively. This allows us to investigate the excited exciton states by photoluminescence upconversion spectroscopy for both monolayer materials. The excitation laser is tuned into resonance with the A:1s transition and we observe emission of excited exciton states up to 200 meV above the laser energy. We demonstrate bias control of the efficiency of this non-linear optical process. At the origin of upconversion our model calculations suggest an exciton-exciton (Auger) scattering mechanism specific to TMD MLs involving an excited conduction band thus generating high energy excitons with small wave-vectors. The optical transitions are further investigated by white light reflectivity, photoluminescence excitation and resonant Raman scattering confirming their origin as excited excitonic states in monolayer thin semiconductors.

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Excitonic properties of semiconducting monolayer and bilayer MoTe2

Cited by 74 publications

References 76 publications

Excitonic complexes and optical gain in two-dimensional molybdenum ditelluride well below the Mott transition

Excitonic complexes and optical gain in two-dimensional molybdenum ditelluride well below the Mott transition

Resonant photonic crystals based on van der Waals heterostructures for effective light pulse retardation

Exciton States in Monolayer MoSe2 and MoTe2 Probed by Upconversion Spectroscopy

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