Effect of Structural Relaxation on the Electronic Structure of Graphene on Hexagonal Boron Nitride

Slotman, Guus J.; Wijk, M. M. van; Zhao, Peichao; Fasolino, A.; Katsnelson, M. I.; Yuan, Shengjun

doi:10.1103/physrevlett.115.186801

Cited by 108 publications

(79 citation statements)

References 33 publications

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“…[21,22] Graphene interactions with h-BN were described with the Kolmogorov Crespi (KC) potential [19] modified as described in Ref. 20, where the strength of the KC potential was doubled for C-N interactions and reduced to 60% for C-B ones. Also, since the C-C bond length depends on the chosen graphene potential, we adopted a slightly rescaled planar simulation cell size so that the graphene/h-BN size ratio exactly matches the experimental ratio ρ.…”

Section: Methodsmentioning

confidence: 99%

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Graphene on h-BN: to align or not to align?

et al. 2017

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The contact strength, adhesion and friction, between graphene and an incommensurate crystalline substrate such as h-BN depends on their relative alignment angle θ. The well established Novaco-McTague (NM) theory predicts for a monolayer graphene on a hard bulk h-BN crystal face a small spontaneous misalignment, here θNM 0.45 degrees which if realized would be relevant to a host of electronic properties besides the mechanical ones. Because experimental equilibrium is hard to achieve, we inquire theoretically about alignment or misalignment by simulations based on dependable state-of-the-art interatomic force fields. Surprisingly at first, we find compelling evidence for θ = 0, i.e., full energy-driven alignment in the equilibrium state of graphene on h-BN. Two factors drive this deviation from NM theory. First, graphene is not flat, developing on h-BN a long-wavelength out-of-plane corrugation. Second, h-BN is not hard, releasing its contact stress by planar contractions/expansions that accompany the interface moiré structure. Repeated simulations by artificially forcing graphene to keep flat, and h-BN to keep rigid, indeed yield an equilibrium misalignment similar to θNM as expected. Subsequent sliding simulations show that friction of graphene on h-BN, small and essentially independent of misalignments in the artificial frozen state, strongly increases in the more realistic corrugated, strain-modulated, aligned state.

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Section: Methodsmentioning

confidence: 99%

“…For each angle we constructed a sample as in Ref. 20 and carefully minimized its classical energy (T = 0), by allowing all atoms to relax their positions, while keeping at the same time the chosen overall alignment angle θ blocked by the periodic boundary conditions.…”

Section: Methodsmentioning

confidence: 99%

Graphene on h-BN: to align or not to align?

et al. 2017

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“…While translation of the top BN with respect to the bottom would change the overall stacking configuration, we observe nearly equivalent transport every ∆θ t = 120 • . This suggests translation does not play a significant role, and that the stacking configuration with no translational offset is the structural ground state at the aligned positions.In graphene aligned to a single BN layer, the staggered sublattice potential of the BN breaks inversion symmetry in the graphene layer for both 0 • and 60 • "aligned" orientations, resulting in a band gap at the PDP whose value is expected to scale with the magnitude of effective superlattice potential [13][14][15][16][17][18][19][20][21][22][23][24][25][26]. We conjecture that the asymmetry between θ t = 0 • and 60 • in our device correlates with the transition between the broken inversion symmetry structure at θ t = θ b = 0 • (Fig.…”

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confidence: 99%

Tunable crystal symmetry in graphene–boron nitride heterostructures with coexisting moiré superlattices

et al. 2019

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In heterostructures consisting of atomically thin crystals layered on top of one another, lattice mismatch or rotation between the layers results in long-wavelength moiré superlattices. These moiré patterns can drive significant band structure reconstruction of the composite material, leading to a wide range of emergent phenomena including superconductivity [1][2][3], magnetism [4], fractional Chern insulating states [5], and moiré excitons [6][7][8][9]. Here, we investigate monolayer graphene encapsulated between two crystals of boron nitride (BN), where the rotational alignment between all three components can be varied. We find that band gaps in the graphene arising from perfect rotational alignment with both BN layers can be modified substantially depending on whether the relative orientation of the two BN layers is 0 or 60 degrees, suggesting a tunable transition between the absence or presence of inversion symmetry in the heterostructure. Small deviations (< 1 • ) from perfect alignment of all three layers leads to coexisting longwavelength moiré potentials, resulting in a highly reconstructed graphene band structure featuring multiple secondary Dirac points. Our results demonstrate that the interplay between multiple moiré patterns can be utilized to controllably modify the electronic properties of the composite heterostructure.The ability to combine diverse vdW materials into a heterostructure enables engineering of new properties not observed in the constituent materials alone. A unique degree of freedom within these vdW heterostructures is the twist angle between layers, and changing this angle can strongly modify the material properties owing to the formation of moiré patterns. In graphene-BN heterostructures, the moiré pattern introduces a spatiallyperiodic effective potential that modifies the graphene band structure, giving rise to emergent secondary Dirac points (SDPs) at finite energy [10][11][12][13] and band gaps at the charge neutrality point and valence band SDP [13][14][15][16][17][18][19][20][21][22][23][24][25][26]. In twisted bilayer graphene (tBLG), correlated insulating states and superconductivity emerge at a twist angle of ∼1.1 • where the lowest energy moiré bands be-come exceptionally flat [1,2,4,27,28]. However, typical vdW heterostructures comprising many flakes possess numerous crystal interfaces, and in principle multiple long-wavelength moiré patterns may coexist within a single heterostructure, likely with profound consequences on moiré-driven physics. For example, topological bands have been shown to potentially arise in tBLG aligned to BN [4]. So far, little has been done to controllably tune the alignment of multiple pairs of crystals within a single device, and it is not well understood how multiple moiré patterns interact to influence the properties of the vdW heterostructure.In a heterostructure where graphene is encapsulated on both sides by BN, there are a number of qualitatively distinct stacking orders that can be realized by independently controlling the twist angle ...

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“…The action of the periodic modulation on electronic structure of graphene in Van der Waals heterostructures includes both changes of on-site electrostatic potential and modulation of metrics via the change of hopping parameters [32,33]. The models of homogeneous lattices take into account only the second effect.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic destruction of the Fermi surface in inhomogeneous holographic lattices

et al. 2020

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We analyze fermionic response of strongly correlated holographic matter in presence of inhomogeneous periodically modulated potential mimicking the crystal lattice. The modulation is sourced by a scalar operator that explicitly breaks the translational symmetry in one direction. We compute the fermion spectral function and show that it either exhibits a well defined Fermi surface with umklapp gaps opening on the Brillouin zone boundary at small lattice wave vector, or, when the wave vector is large, the Fermi surface is anisotropically deformed and the quasiparticles get significantly broadened in the direction of translation symmetry breaking.Making use of the ability of our model to smoothly extrapolate to the homogeneous Q-lattice like setup, we show that this novel effect is not due to the periodic modulation of the potential and Umklapp physics, but rather due to the anisotropic features of the holographic horizon. That means it encodes novel physics of strongly correlated critical systems which may be relevant for phenomenology of exotic states of electron matter.

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Effect of Structural Relaxation on the Electronic Structure of Graphene on Hexagonal Boron Nitride

Cited by 108 publications

References 33 publications

Graphene on h-BN: to align or not to align?

Graphene on h-BN: to align or not to align?

Tunable crystal symmetry in graphene–boron nitride heterostructures with coexisting moiré superlattices

Anisotropic destruction of the Fermi surface in inhomogeneous holographic lattices

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