Pseudomagnetic fields and triaxial strain in graphene

Settnes, Mikkel; Power, Stephen R.; Jauho, Antti–Pekka

doi:10.1103/physrevb.93.035456

Cited by 71 publications

(68 citation statements)

References 63 publications

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“…In the continuum description, the effect of the deformation usually appears as an inhomogeneous pseudo-gauge field [21,[31][32][33]. The hopping modifications give origin to gauge fields in the Dirac equation [34], with the pseudo vector potential written in terms of the strain tensor elements,…”

Section: Structures and Modelmentioning

confidence: 99%

Gap engineering in strained fold-like armchair graphene nanoribbons

et al. 2017

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Strain fold-like deformations on armchair graphene nanoribbons (AGNRs) can be properly engineered in experimental setups, and could lead to a new controlling tool for gaps and transport properties. Here, we analyze the electronic properties of folded AGNRs relating the electronic responses and the mechanical deformation. An important and universal parameter for the gap engineering is the ribbon percent width variation, i.e., the difference between the deformed and undeformed ribbon widths. AGNRs bandgap can be tuned mechanically in a well defined bounded range of energy values, eventually leading to a metallic system. This characteristic provides a new controllable degree of freedom that allows manipulation of electronic currents. We show that the numerical results are analytically predicted by solving the Dirac equation for the strained system.

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Section: Structures and Modelmentioning

confidence: 99%

Gap engineering in strained fold-like armchair graphene nanoribbons

et al. 2017

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“…The DOS is dominated by the zeroth pLL, which induces a strong sublattice polarization 6,22,47 . Here the decrease of D(E, t) with time reveals the onset of localization effects.…”

Section: Localization Effectsmentioning

confidence: 99%

“…Because the low-energy states are mostly polarized on the B-sublattice, they are strongly affected by short-range valley-mixing effects induced by A-vacancies, leading to stronger localization effects (blue curve on Figure 5). Indeed, unlike the zeroth order Landau level caused by a real magnetic field where valleys are located on opposite sublattices, the valleys are concentrated on the same sublattice in the presence of a pseudomagnetic field 6 . Finally, even if the A-vacancies yield stronger localization effects, they concurrently lead to longer meanfree paths, when compared to B-vacancies.…”

Section: Energy-dependent Random Disorder Effectmentioning

confidence: 99%

“…It has been shown that low-energy states are preferentially located inside the deformed region, while high-energy states correspond to states outside the bubbles 68 . Furthermore, the zeroth pLL induces sublattice polarization 22 , where the preferred sublattice depends on the deformation direction 6 . This sublattice polarization of the first Landau level is a unique feature of pseudomagnetic fields.…”

Section: Energy-dependent Random Disorder Effectmentioning

confidence: 99%

“…However, compared to a real magnetic field, the formation of a pseudomagnetic field preserves time reversal symmetry, having an opposite sign in the two inequivalent K and K' valleys [4][5][6] . This leads to different behavior than for real magnetic field especially when introducing disorder.…”

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confidence: 99%

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Quantum transport in graphene in presence of strain-induced pseudo-Landau levels

Settnes¹,

Leconte²,

Vargas³

et al. 2016

2D Mater.

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We report on mesoscopic transport fingerprints in disordered graphene caused by strain-field induced pseudomagnetic Landau levels (pLLs). Efficient numerical real space calculations of the Kubo formula are performed for an ordered network of nanobubbles in graphene, creating pseudomagnetic fields up to several hundreds of Tesla, values inaccessible by real magnetic fields. Strain-induced pLLs yield enhanced scattering effects across the energy spectrum resulting in lower mean free path and enhanced localization effects. In the vicinity of the zeroth order pLL, we demonstrate an anomalous transport regime, where the mean free paths increases with disorder. We attribute this puzzling behavior to the low-energy sub-lattice polarization induced by the zeroth order pLL, which is unique to pseudomagnetic fields preserving time-reversal symmetry. These results, combined with the experimental feasibility of reversible deformation fields, open the way to tailor a metal-insulator transition driven by pseudomagnetic fields.Inhomogeneous lattice deformations in graphene generate an effective gauge field modulating the electronic spectrum 1-3 . However, compared to a real magnetic field, the formation of a pseudomagnetic field preserves time reversal symmetry, having an opposite sign in the two inequivalent K and K' valleys 4-6 . This leads to different behavior than for real magnetic field especially when introducing disorder. Experimentally, scanning-tunneling measurements on graphene nanobubbles have revealed an electronic spectrum consisting of pseudo-Landau levels (pLL), including a zero-energy peak, showing that moderate spatial deformations can introduce pseudomagnetic field values reaching hundreds of Tesla 7-9 . Pseudomagnetic fields (PMF) have also been analyzed in deformed crystals by an atomically controlled arrangement of CO molecules on a gold surface 10 , graphene on Ir with intercalated Pb monolayer islands 11 , or have been harnessed for designing innovative electronic and photonic graphene devices 12-17 .However, the intrinsic quantum transport fingerprints of graphene in presence of pseudomagnetic fields still needs investigation, especially in disordered systems. In particular, random strain fluctuations are believed to be the dominating disorder source in high-quality onsubstrate graphene devices 18,19 . A signature of the pseudomagnetic n = 0 pLL state has been predicted for stretched graphene ribbons in the form of a quadruplet low-energy conductance resonance split by edge-induced valley mixing16 , but its experimental confirmation remains challenging, and the variable range of transport features in deformed graphene still require further indepth exploration.Here we study the effect of pLLs, generated by an ordered network of graphene nanobubbles (or pseudomagnetic dots), using an efficient real space Kubo quantum transport methodology. We consider samples containing electron-hole puddles caused by substrate interactions where the presence of pLLs leads to several anomalous transport features resultin...

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Strained Graphene Structures: From Valleytronics to Pressure Sensing

Milovanović

Peeters

2018

NATO Science for Peace and Security Series A: Chemistry and Biology

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Due to its strong bonds graphene can stretch up to 25% of its original size without breaking. Furthermore, mechanical deformations lead to the generation of pseudo-magnetic fields (PMF) that can exceed 300 T. The generated PMF has opposite direction for electrons originating from different valleys. We show that valley-polarized currents can be generated by local straining of multi-terminal graphene devices. The pseudo-magnetic field created by a Gaussian-like deformation allows electrons from only one valley to transmit and a current of electrons from a single valley is generated at the opposite side of the locally strained region. Furthermore, applying a pressure difference between the two sides of a graphene membrane causes it to bend/bulge resulting in a resistance change. We find that the resistance changes linearly with pressure for bubbles of small radius while the response becomes non-linear for bubbles that stretch almost to the edges of the sample. This is explained as due to the strong interference of propagating electronic modes inside the bubble. Our calculations show that high gauge factors can be obtained in this way which makes graphene a good candidate for pressure sensing. arXiv:1711.07904v1 [cond-mat.mes-hall]

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Pseudomagnetic fields and triaxial strain in graphene

Cited by 71 publications

References 63 publications

Gap engineering in strained fold-like armchair graphene nanoribbons

Gap engineering in strained fold-like armchair graphene nanoribbons

Quantum transport in graphene in presence of strain-induced pseudo-Landau levels

Strained Graphene Structures: From Valleytronics to Pressure Sensing

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