Double Moiré with a Twist: Supermoiré in Encapsulated Graphene

Anđelković, Miša; Milovanović, S. P.; Covaci, Lucian; Peeters, F. M.

doi:10.1021/acs.nanolett.9b04058

Cited by 69 publications

(58 citation statements)

References 39 publications

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“…These coexisting moiré patterns with different wavelengths should, in principle, interfere, resulting in a second-order (composite) moiré pattern, as reported in experimental (38)(39)(40) and theoretical studies (41,42). From the two SDPs, we calculated the corresponding twist angles to be 0.24° and 0.38° (see Materials and Methods).…”

Section: Discussionmentioning

confidence: 92%

In situ manipulation of van der Waals heterostructures for twistronics

Yang

Yin

et al. 2020

Sci. Adv.

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In van der Waals heterostructures, electronic bands of two-dimensional (2D) materials, their nontrivial topology, and electron-electron interactions can be markedly changed by a moiré pattern induced by twist angles between different layers. This process is referred to as twistronics, where the tuning of twist angle can be realized through mechanical manipulation of 2D materials. Here, we demonstrate an experimental technique that can achieve in situ dynamical rotation and manipulation of 2D materials in van der Waals heterostructures. Using this technique, we fabricated heterostructures where graphene is perfectly aligned with both top and bottom encapsulating layers of hexagonal boron nitride. Our technique enables twisted 2D material systems in one single stack with dynamically tunable optical, mechanical, and electronic properties.

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Section: Discussionmentioning

confidence: 92%

In situ manipulation of van der Waals heterostructures for twistronics

Yang

Yin

et al. 2020

Sci. Adv.

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“…To quantitatively analyse them, a phenomenological model was given, which, for simplicity, assumes that the −4 n 0 filling corresponds a fixed h-BN/graphene moiré with a smaller twist (wavelength L α ), and all extra peaks are from another moiré with a larger twist (wavelength L β ). Thus, one can then extract and fix L α , and solve L β using the formula 17 , 23 where a is graphene’s lattice constant, l β is the reciprocal lattice vector of L β , and δ is the lattice mismatch between graphene and h-BN 24 . Experimentally, L α can be larger than the theoretical maximum of 13.8 nm in a graphene/h-BN superlattice, due to possibly existing strains in the heterostructures 17 , 25 .…”

Section: Resultsmentioning

confidence: 99%

“…Experimentally, L α can be larger than the theoretical maximum of 13.8 nm in a graphene/h-BN superlattice, due to possibly existing strains in the heterostructures 17 , 25 . The above-mentioned analytical formula yields six solutions at each side of the charge neutrality, because of the six vectors formed by the two of moiré Brillouin zone from top and bottom surfaces of graphene 17 , 23 . With this method, one can have access to the relatively precise twist angles in measured samples via their resistive peaks in the field-effect spectra.…”

Section: Resultsmentioning

confidence: 99%

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Correlated states in doubly-aligned hBN/graphene/hBN heterostructures

et al. 2021

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Interfacial moiré superlattices in van der Waals vertical assemblies effectively reconstruct the crystal symmetry, leading to opportunities for investigating exotic quantum states. Notably, a two-dimensional nanosheet has top and bottom open surfaces, allowing the specific case of doubly aligned super-moiré lattice to serve as a toy model for studying the tunable lattice symmetry and the complexity of related electronic structures. Here, we show that by doubly aligning a graphene monolayer to both top and bottom encapsulating hexagonal boron nitride (h-BN), multiple conductivity minima are observed away from the main Dirac point, which are sensitively tunable with respect to the small twist angles. Moreover, our experimental evidences together with theoretical calculations suggest correlated insulating states at integer fillings of −5, −6, −7 electrons per moiré unit cell, possibly due to inter-valley coherence. Our results provide a way to construct intriguing correlations in 2D electronic systems in the weak interaction regime.

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“…Heavily corrugated Moiré in gr/Ru(0001) shows localized states close to the Fermilevel 19 . It has been shown that lattice relaxation, (which leads to a corrugated surface) is an important parameter to understand the origin of the gap 20,21 and flat-band formation 22 in gr/h-BN systems. The importance of the relaxation was also pointed out for low angle twisted bilayer graphene (TBLG), where an energy gap of up to 20 meV opens at the superlattice subband edge 18,23 , which is also found in experiments 15,24 and is needed to fully describe the Mott-physics of the system.…”

Section: Introductionmentioning

confidence: 99%

Ultra-flat twisted superlattices in 2D heterostructures

et al. 2020

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Moiré-superlattices are ubiquitous in 2D heterostructures, strongly influencing their electronic properties. They give rise to new Dirac cones and are also at the origin of the superconductivity observed in magic-angle bilayer graphene. The modulation amplitude (corrugation) is an important yet largely unexplored parameter in defining the properties of 2D superlattices. The generally accepted view is that the corrugation monotonically decreases with increasing twist angle, while its effects on the electronic structure diminish as the layers become progressively decoupled. Here we found by lattice relaxation of around 8000 different Moiré-superstructures using high scale Classical Molecular Simulations combined with analytical calculations, that even a small amount of external strain can substantially change this picture, giving rise to more complex behavior of superlattice corrugation as a function of twist angle. One of the most surprising findings is the emergence of an ultra-flat phase that can be present for arbitrary small twist angle having a much lower corrugation level than the decoupled phase at large angles. Furthermore, Moiré-phase maps evidence that the state with no external strain is located in the close vicinity of a triple Moiré-phase boundary, implying that very small external strain variations can cause drastic changes in the realized superlattice morphology and corrugation. This renders the practical realization of 2D heterostructures with large-area homogeneous superlattice morphology highly challenging.

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Double Moiré with a Twist: Supermoiré in Encapsulated Graphene

Cited by 69 publications

References 39 publications

In situ manipulation of van der Waals heterostructures for twistronics

In situ manipulation of van der Waals heterostructures for twistronics

Correlated states in doubly-aligned hBN/graphene/hBN heterostructures

Ultra-flat twisted superlattices in 2D heterostructures

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