Enhanced interactions of interlayer excitons in free-standing heterobilayers

Sun, Xueqian; Zhu, Yi; Qin, Hao; Liu, Boqing; Tang, Yuqi; Lü, Tie-Yu; Rahman, Saidur; Yildirim, Tanju; Lu, Yuerui

doi:10.1038/s41586-022-05193-z

Cited by 44 publications

(44 citation statements)

References 46 publications

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“…The method for PLEF calculation has been previously reported. − The linear fitting of power-dependent PL spectra of InSe in and off cavity (Figure d) yielded slopes of 1.05 and 1.07, respectively, confirming the generation of a PL signal from OP orientation bright excitons in InSe. Furthermore, the PL peak of InSe shifted to a blue direction as excitation power increased, which is similar to the regulation observed for interlayer excitons in two-dimensional heterobilayers . The inset shows the PLEF as a function of excitation power and PLEF is large and remains relatively uniform.…”

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confidence: 77%

“…Furthermore, the PL peak of InSe shifted to a blue direction as excitation power increased, which is similar to the regulation observed for interlayer excitons in two-dimensional heterobilayers. 44 The inset shows the PLEF as a function of excitation power and PLEF is large and remains relatively uniform. Simulations of the local electric field intensities of an InSeembedded plasmonic nanocavity with different thicknesses (Supplementary Figure 2) demonstrated that the thickness of the embedded dielectric layer can impact the resonance wavelength, local electric field intensity, and Purcell effect of the plasmonic nanocavity.…”

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confidence: 99%

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Giant Out-of-Plane Exciton Emission Enhancement in Two-Dimensional Indium Selenide via a Plasmonic Nanocavity

Bao

et al. 2023

Nano Lett.

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Out-of-plane (OP) exciton-based emitters in twodimensional semiconductor materials are attractive candidates for novel photonic applications, such as radially polarized sources, integrated photonic chips, and quantum communications. However, their low quantum efficiency resulting from forbidden transitions limits their practicality. In this work, we achieve a giant enhancement of up to 34000 for OP exciton emission in indium selenide (InSe) via a designed Ag nanocube-over-Au film plasmonic nanocavity. The large photoluminescence enhancement factor (PLEF) is attributed to the induced OP local electric field (E z ) within the nanocavity, which facilitates effective OP exciton− plasmon interaction and subsequent tremendous enhancement. Moreover, the nanoantenna effect resulting from the effective interaction improves the directivity of spontaneous radiation. Our results not only reveal an effective photoluminescence enhancement approach for OP excitons but also present an avenue for designing on-chip photonic devices with an OP dipole orientation.

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confidence: 77%

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confidence: 99%

Giant Out-of-Plane Exciton Emission Enhancement in Two-Dimensional Indium Selenide via a Plasmonic Nanocavity

Bao

et al. 2023

Nano Lett.

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“…10,11 Such a periodic modulation is referred to as the Moirésuperlattice (MSL) and can modify the atomic structure, coupling strength, energy, and optical selection rules. 10,12,13 This provides an exceptional degree of freedom to tune the optical and electronic properties of TMDs at the atomic limit.…”

Section: Introductionmentioning

confidence: 99%

“…Atomically thin two-dimensional layered materials, namely, transition metal chalcogenides (TMDs), have drawn extensive interest over the past decades due to their exclusive physical properties, serving as the ideal platform to explore a rich variety of physics and device applications. − van der Waals (vdW) heterostructures of monolayer TMDs fabricated from mechanical stacking or chemical growth can bring fundamental changes to the electronic and photonic properties. , In particular, they can harvest incommensurate patterns, originating from the relative twist angle during the stacking of the layered materials. , This is reinforced by the different lattice constant of the two constituent materials being rotated with respect to each other, which also facilitates a weak vdW force at the monolayer interface. , Such a periodic modulation is referred to as the Moiré superlattice (MSL) and can modify the atomic structure, coupling strength, energy, and optical selection rules. ,, This provides an exceptional degree of freedom to tune the optical and electronic properties of TMDs at the atomic limit.…”

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confidence: 99%

Extraordinary Phonon Displacement and Giant Resonance Raman Enhancement in WSe₂/WS₂ Moiré Heterostructures

et al. 2022

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Twisted van der Waals heterostructures are known to induce surprisingly diverse and intriguing phenomena, such as correlated electronic phase and unconventional optical properties. This can be realized by controlled rotation of adjacent atomic planes, which provides an uncommon way to manipulate inelastic light–matter interactions. Here, we discover an extraordinary blue shift of 5–6 wavenumbers for high-frequency phonon modes in WS2/WSe2 twisted heterobilayers, captured meticulously using Raman spectroscopy. Phonon spectra displace rapidly over a subtle change in interlayer twist angle owing to heterostrain and atomic reconstruction from the Moiré pattern. First-order linear coefficients of the phonon modes in twisted heterostructures are further found to increase largely compared to their monolayer counterpart and vary immensely with the twist angle. Exceptional and extravagant enhancement of up to 50-fold is observed in the Raman vibrational intensity at a specific twist angle; this is largely influenced by the resonance process derived from a simple critical twist angle model. In addition, we depict how the resonance can be modulated by changing the thermal conditions and also the stacking angle. Therefore, our work further highlights the twist-driven phonon dynamics in pristine two-dimensional heterostructures, adding vital insight into Moiré physics and promoting comprehensive understanding of structural and optical properties in Moiré superlattices.

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“…By tuning the effective interlayer distance, the interaction between interlayer excitons can be altered from dipole repulsion to attraction, leading to the formation of a stable biexciton phase 19 . Theoretical predictions suggest that dipole-dipole interactions can occur in both parallel and antiparallel configurations [20][21][22] , but only repulsive interactions in parallel configurations have been observed experimentally [23][24][25][26] . Strain engineering is a powerful technique for designing quantum devices and enhancing the coherence of interlayer excitons by combining strong light-matter interactions with excitons, thereby improving their quantum luminescence efficiency.…”

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Observation of Robust Interlayer Biexcitons in Twisted Homobilayer Superlattices

Zheng

Xie

et al. 2023

Preprint

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Moiré superlattices are formed by stacking 2D materials with a twist angle and have recently gained attention as a platform for investigating the interactions and correlations of moiré-trapped interlayer excitons (IXs). However, understanding these excitons remains challenging, as theoretical predictions suggest the existence of both parallel and antiparallel dipole-dipole interactions, while only repulsive interactions with a parallel configuration have been experimentally observed. Here, we investigate the localization of strain-induced moiré interlayer excitons in twisted transition metal dichalcogenide (TMDC) superlattices. Our results reveal that modulating the moiré trap in strain-engineered homobilayers leads to a higher density and emission efficiency of IXs, while also enhancing dipole-dipole interactions. In particular, we observe a transition in the nature of the moiré interlayer exciton-dipole interaction from repulsion to attraction in a twist-angle homostructure, resulting in a stable interlayer biexciton (IXX) phase with an antiparallel configuration, which had only been theoretically predicted before. Moreover, the moiré trap in homobilayers can be modulated by adjusting the spacing of the Au nanoarrays, which enabled us to achieve IXX emission up to 150 K, the highest temperature reported to date. This breakthrough is expected to pave the way for the observation of a Bose-Einstein condensate at room temperature. Our findings provide new opportunities for studying correlated many-body systems and have implications for developing novel optoelectronic devices and controllable nonlinear optics.

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Enhanced interactions of interlayer excitons in free-standing heterobilayers

Cited by 44 publications

References 46 publications

Giant Out-of-Plane Exciton Emission Enhancement in Two-Dimensional Indium Selenide via a Plasmonic Nanocavity

Giant Out-of-Plane Exciton Emission Enhancement in Two-Dimensional Indium Selenide via a Plasmonic Nanocavity

Extraordinary Phonon Displacement and Giant Resonance Raman Enhancement in WSe₂/WS₂ Moiré Heterostructures

Observation of Robust Interlayer Biexcitons in Twisted Homobilayer Superlattices

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Enhanced interactions of interlayer excitons in free-standing heterobilayers

Cited by 44 publications

References 46 publications

Giant Out-of-Plane Exciton Emission Enhancement in Two-Dimensional Indium Selenide via a Plasmonic Nanocavity

Giant Out-of-Plane Exciton Emission Enhancement in Two-Dimensional Indium Selenide via a Plasmonic Nanocavity

Extraordinary Phonon Displacement and Giant Resonance Raman Enhancement in WSe2/WS2 Moiré Heterostructures

Observation of Robust Interlayer Biexcitons in Twisted Homobilayer Superlattices

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Extraordinary Phonon Displacement and Giant Resonance Raman Enhancement in WSe₂/WS₂ Moiré Heterostructures