Intralayer charge-transfer moiré excitons in van der Waals superlattices

Naik, Mit H.; Regan, Emma C.; Zhang, Zuocheng; Chan, Yang-Hao; Li, Zhenglu; Wang, Danqing; Yoon, Yeoreum; Ong, Chin Shen; Zhao, Wenyu; Zhao, Sihan; Utama, M. Iqbal Bakti; Gao, Beini; Wei, Xin; Sayyad, Mohammed; Yumigeta, Kentaro; Watanabe, Kenji; Taniguchi, Takashi; Tongay, Sefaattin; Jornada, Felipe H. da; Wang, Feng; Louie, Steven G.

doi:10.1038/s41586-022-04991-9

Cited by 90 publications

(62 citation statements)

References 56 publications

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“…Usually, when a lattice-mismatched TMDC heterostructure is formed by use of thermodynamics-based growth techniques such as chemical vapor deposition, the heterostructure does not reconstruct (10). The unexpectedly large in-plane structural reconstruction we observed in the R-stacked van der Waals interfaces was recently predicted by theory, and the associated inhomogeneous strain in the individual layers is responsible for the formation of flat electronic bands (24) and spatially modulated excitonic states (9).…”

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confidence: 78%

“…The splitting of the WSe 2 A exciton peak into three peaks in the WS 2 -WSe 2 moiré superlattice is predicted ( 9 ) to be a result of the strong in-plane structural reconstruction observed in ADF-STEM measurements (Fig. 1), which is unlike other moiré systems in which layer hybridization can also contribute to the moiré-exciton fine structure ( 7 ).…”

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confidence: 96%

“…For example, the moiré superlattice of semiconducting transitionmetal dichalcogenides (TMDCs) have been predicted to form a topologically protected lattice of bound electron-hole pairs or excitons that can act as a model system for quantum simulations and technologies (2)(3)(4). Recent optical spectroscopy studies have found signatures of interlayer and intralayer moiré excitons in TMDC heterostructures (5)(6)(7)(8)(9), investigated exciton diffusion in a superlattice potential (10), and found evidence for the cooperative nature of moiré excitons (11). An important parameter less well studied is the nature of the excitons at the nanoscale level.…”

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confidence: 99%

“…S24). The GW-BSE calculation for the large-area moiré superlattice was made possible by a recently developed pristine unit cell matrix projection (PUMP) method (9). The wave function that describes a moiré exciton state S is a linear combination of valence-to-conduction transitions in the Brillouin zone:…”

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confidence: 99%

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Hyperspectral imaging of exciton confinement within a moiré unit cell with a subnanometer electron probe

Susarla

Naik

Blach

et al. 2022

Science

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Electronic and optical excitations in two-dimensional systems are distinctly sensitive to the presence of a moiré superlattice. We used cryogenic transmission electron microscopy and spectroscopy to simultaneously image the structural reconstruction and associated localization of the lowest-energy intralayer exciton in a rotationally aligned WS 2 -WSe 2 moiré superlattice. In conjunction with optical spectroscopy and ab initio calculations, we determined that the exciton center-of-mass wave function is confined to a radius of approximately 2 nanometers around the highest-energy stacking site in the moiré unit cell. Our results provide direct evidence that atomic reconstructions lead to the strongly confining moiré potentials and that engineering strain at the nanoscale will enable new types of excitonic lattices.

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confidence: 78%

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confidence: 96%

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confidence: 99%

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confidence: 99%

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Hyperspectral imaging of exciton confinement within a moiré unit cell with a subnanometer electron probe

Susarla

Naik

Blach

et al. 2022

Science

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“…Recently, the twisted van der Waals heterostructured superlattices have attracted significant attention as they provide a powerful and attractive platform for exploring the new physics of novel condensed matter [1][2][3][4][5][6] . Vertically stacked 2D materials can generate periodic moiré superlattices due to lattice mismatches or twist angles 7 .…”

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confidence: 99%

Localization-enhanced moiré exciton in twisted transition metal dichalcogenide heterotrilayer superlattices

Liu

Zheng

et al. 2022

Preprint

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Moiré superlattice created by the stacking of twisted 2D layered materials have become a new platform for the study of quantum optics. The strong coupling of moiré superlattices can generate flat minibands that enhance electronic interactions and produce a variety of fascinating strongly correlated states such as non-conventional superconductivity, Mott insulating states and moiré excitons. However, the influence between the adjustment and localization of moiré excitons in Van der Waals heterostructures has not been the subject of experimental investigations. Here we report experimental evidence of the localization-enhanced moiré excitons in the twisted WSe2/WS2/WSe2 heterotrilayer with type-II band alignments. At low temperature, we observed multiple excitons splitting phenomena in the twisted WSe2/WS2/WSe2 heterotrilayer, manifesting as multiple sharp emission lines, contrasting strongly with the moiré excitonic behavior of the twisted WSe2/WS2 heterobilayer (the linewidth is 4 times narrower). This is primarily because the enhancement of the two moiré potentials in the twisted heterotrilayer enables the moiré excitons at the highly localized interface. Furthermore, the changes in temperature, laser power and valley polarization further demonstrate the confinement effect of moiré potential on moiré excitons. Our findings provide a new way for the localization of moiré excitons in twist-angle heterostructures, facilitating the development of coherent quantum light emitters.

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Homo‐Site Nucleation Growth of Twisted Bilayer MoS₂ with Commensurate Angles

Zhou,

Huang,

Zhao

et al. 2024

Advanced Materials

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Moiré superlattices, composed of two layers of transition metal dichalcogenides with a relative twist angle, provide a novel platform for exploring the correlated electronic phases and excitonic physics. Here, a gas‐flow perturbation chemical vapor deposition (CVD) approach is demonstrated to directly grow MoS2 bilayer with versatile twist angles. It is found that the formation of twisted bilayer MoS2 homostructures sensitively depends on the gas‐flow perturbation modes, correspondingly featuring the nucleation sites of the second layer at the same (homo‐site) as or at the different (hetero‐site) from that of the first layer. The commensurate twist angle of ≈22° in homo‐site nucleation strategy accounts for ≈16% among the broad range of twist angles due to its low formation energy, which is in consistence with the theoretical calculation. More importantly, moiré interlayer excitons with the enhanced photoluminescence (PL) intensity and the prolonged lifetime are evidenced in the twisted bilayer MoS2 with a commensurate angle of 22°, which is owing to the reason that the strong moiré potential facilitates the interlayer excitons to be trapped in the moiré superlattices. The work provides a feasible route to controllably built twisted MoS2 homostructures with strong moiré potential to investigate the correlated physics in twistronics systems.

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Intralayer charge-transfer moiré excitons in van der Waals superlattices

Cited by 90 publications

References 56 publications

Hyperspectral imaging of exciton confinement within a moiré unit cell with a subnanometer electron probe

Hyperspectral imaging of exciton confinement within a moiré unit cell with a subnanometer electron probe

Localization-enhanced moiré exciton in twisted transition metal dichalcogenide heterotrilayer superlattices

Homo‐Site Nucleation Growth of Twisted Bilayer MoS₂ with Commensurate Angles

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Intralayer charge-transfer moiré excitons in van der Waals superlattices

Cited by 90 publications

References 56 publications

Hyperspectral imaging of exciton confinement within a moiré unit cell with a subnanometer electron probe

Hyperspectral imaging of exciton confinement within a moiré unit cell with a subnanometer electron probe

Localization-enhanced moiré exciton in twisted transition metal dichalcogenide heterotrilayer superlattices

Homo‐Site Nucleation Growth of Twisted Bilayer MoS2 with Commensurate Angles

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Homo‐Site Nucleation Growth of Twisted Bilayer MoS₂ with Commensurate Angles