Topologically confined states at corrugations of gated bilayer graphene

Pelc, Marta; Jaskólski, W.; Ayuela, Andrés; Chico, Leonor

doi:10.1103/physrevb.92.085433

Cited by 32 publications

(50 citation statements)

References 69 publications

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“…Similar arguments apply for TDBG structures with C 3 symmetry, which also have at most two-dimensional irreps. In fact, the sublattice-andlayer-exchange symmetry is broken by any perturbation that allows to distinguish between layers, such as a potential difference [41][42][43] or another layer(s) coupled with a twist 23 . This symmetry breaking results in the opening of a gap between the AB-related bands, due to the different atomic coordination environments of the two AB layers.…”

Section: Resultsmentioning

confidence: 99%

Flat bands and gaps in twisted double bilayer graphene

et al. 2020

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We present electronic structure calculations of twisted double bilayer graphene (TDBG): A tetralayer graphene structure composed of two AB-stacked graphene bilayers with a relative rotation angle between them. Using first-principles calculations, we find that TDBG is semiconducting with a band gap that depends on the twist angle, that can be tuned by an external electric field. The gap is consistent with TDBG symmetry and its magnitude is related to surface effects, driving electron transfer from outer to inner layers. The surface effect competes with an energy upshift of localized states at inner layers, giving rise to the peculiar angle dependence of the band gap, which reduces at low angles. For these low twist angles, the TDBG develops flat bands, in which electrons in the inner layers are localized at the AA regions, as in twisted bilayer graphene. arXiv:1911.01347v1 [cond-mat.mes-hall]

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Section: Resultsmentioning

confidence: 99%

Flat bands and gaps in twisted double bilayer graphene

et al. 2020

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“…Importantly, when a domain wall (DW) divides bilayer graphene into AB and BA stacking domains, a pair of states appears at each valley, connecting the valence and conduction band continua through the energy gap ( Fig. 1 right) [21][22][23]. These gapless states are topologically protected if the valley index is conserved.…”

Section: Introductionmentioning

confidence: 99%

Controlling the layer localization of gapless states in bilayer graphene with a gate voltage

et al. 2018

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Experiments in gated bilayer graphene with stacking domain walls present topological gapless states protected by no-valley mixing. Here we research these states under gate voltages using atomistic models, which allow us to elucidate their origin. We find that the gate potential controls the layer localization of the two states, which switches non-trivially between layers depending on the applied gate voltage magnitude. We also show how these bilayer gapless states arise from bands of single-layer graphene by analyzing the formation of carbon bonds between layers. Based on this analysis we provide a model Hamiltonian with analytical solutions, which explains the layer localization as a function of the ratio between the applied potential and interlayer hopping. Our results open a route for the manipulation of gapless states in electronic devices, analogous to the proposed writing and reading memories in topological insulators.

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“…Furthermore, it has been recently shown that slightly twisting the two layers dramatically changes the band structure, allowing the observation of unconventional superconductivity 8 and Mott insulating behavior 18 . An addition to these diverse properties of graphene bilayers are the recently identified topologically protected states at boundaries between AB and BA stacked graphene bilayers [19][20][21][22] . In thicker graphene flakes, the physics can be expected to be even richer, since naturally two stable forms of stacking, Bernal (or ABA, Fig.…”

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Anisotropic Strain-Induced Soliton Movement Changes Stacking Order and Band Structure of Graphene Multilayers: Implications for Charge Transport

Geisenhof

Winterer

Wakolbinger

et al. 2019

ACS Appl. Nano Mater.

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The crystal structure of solid-state matter greatly affects its electronic properties. For example in multilayer graphene, precise knowledge of the lateral layer arrangement is crucial, since the most stable configurations, Bernal and rhombohedral stacking, exhibit very different electronic properties.Nevertheless, both stacking orders can coexist within one flake, separated by a strain soliton that can host topologically protected states. Clearly, accessing the transport properties of the two stackings and the soliton is of high interest. However, the stacking orders can transform into one another and therefore, the seemingly trivial question how reliable electrical contact can be made to either stacking order can a priori not be answered easily. Here, we show that manufacturing metal contacts to multilayer graphene can move solitons by several µm, unidirectionally enlarging Bernal domains due to arising mechanical strain. Furthermore, we also find that during dry transfer of multilayer graphene onto hexagonal Boron Nitride, such a transformation can happen. Using density functional theory modeling, we corroborate that anisotropic deformations of the multilayer graphene lattice decrease the rhombohedral stacking stability. Finally, we have devised systematics to avoid soliton movement, and how to reliably realize contacts to both stacking configurations.

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Topologically confined states at corrugations of gated bilayer graphene

Cited by 32 publications

References 69 publications

Flat bands and gaps in twisted double bilayer graphene

Flat bands and gaps in twisted double bilayer graphene

Controlling the layer localization of gapless states in bilayer graphene with a gate voltage

Anisotropic Strain-Induced Soliton Movement Changes Stacking Order and Band Structure of Graphene Multilayers: Implications for Charge Transport

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