A family of finite-temperature electronic phase transitions in graphene multilayers

Nam, Young Woo; Ki, Dong–Keun; Soler-Delgado, David; Morpurgo, Alberto F.

doi:10.1126/science.aar6855

Cited by 43 publications

(54 citation statements)

References 61 publications

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“…Even in this case, the magnitude and the behavior with thickness of the (pseudo) gaps disagree with experimental data given in Ref. [23].…”

Section: Even Number Of Layerscontrasting

confidence: 73%

“…The pseudogap is larger for N = 3 than for N = 7, in qualitative disagreement with the gap inferred from transport data in Ref. [23].…”

Section: Odd Number Of Layerscontrasting

confidence: 59%

“…The situation is similar for Bernal stacking, as several measurements suggest the occurrence of a gapped state on suspended samples [21][22][23][24]. Among them, a very recent paper [23] show that all N-layer Bernal suspended graphene flakes with 2 N 7 are insulating or pseudogapped. Specifically, the resistance at the charge neutrality point of suspended flakes with N = 2, 4, 6 is in the range 5 × 10 3 to 5 × 10 5 k at T = 0.25 K, monotonically increasing with thickness.…”

Section: Introductionmentioning

confidence: 68%

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Hybrid-functional electronic structure of multilayer graphene

et al. 2020

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Multilayer graphene with rhombohedral and Bernal stacking is supposed to be metallic, as predicted by density functional theory calculations using semilocal functionals. However, recent angular resolved photoemission and transport data have questioned this point of view. In particular, rhombohedral flakes are suggested to be magnetic insulators, a view supported also by hybrid-functional calculations. Bernal flakes composed of an even number of layers are insulating (for N 6), while those composed of an odd number of layers are pseudogapped (for N 7). Here, by systematically benchmarking with plane-waves codes, we develop very accurate all-electron Gaussian basis sets for graphene multilayers, allowing a precise description of the electronic structure in the 100 meV energy range from the Fermi energy at the hybrid-functional level. We find, in agreement with our previous calculations, that rhombohedral stacked multilayers are gapped and magnetic. However, the valence band curvature and the details of the electronic structure at the ∼10 meV scale show a dependence on the basis set. A substantially extended basis set is needed to describe the long-range interlayer interactions and, consequently, to correctly reproduce the effective mass of the valence band top at the K point. In the case of Bernal stacking, we show that exact exchange gaps the flakes composed by four layers and opens pseudogaps for N = 3, 6, 7, 8. However, the gap or pseudogap size and its behavior as a function of thickness are not compatible with experimental data. Moreover, hybrid functionals lead to a metallic solution for five layers and a magnetic ground state for five, six, and eight layers. Magnetism is very weak with practically no effect on the electronic structure and the magnetic moments are mostly concentrated in the central layers. Our hybridfunctional calculations on trilayer Bernal graphene are in excellent agreement with GW results. For thicker multilayers, our calculations are a benchmark for many-body theoretical modeling of the low energy electronic structure.

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“…Even in this case, the magnitude and the behavior with thickness of the (pseudo) gaps disagree with experimental data given in Ref. [23].…”

Section: Even Number Of Layerscontrasting

confidence: 73%

“…The pseudogap is larger for N = 3 than for N = 7, in qualitative disagreement with the gap inferred from transport data in Ref. [23].…”

Section: Odd Number Of Layerscontrasting

confidence: 59%

Section: Introductionmentioning

confidence: 68%

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Hybrid-functional electronic structure of multilayer graphene

et al. 2020

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“…Experiments in bulk graphite are consistent with a value γ 2 ≈ −0.02 eV, see, for instance [46,47]. On the other hand, recent measurements on 4-8 Bernal-stacked multilayers [48][49][50][51] suggest that the second-nearest-neighbor interlayer hopping is much smaller, γ 2 ∼ 0.…”

Section: Twisted Stacking Fault In Bulk Graphitesupporting

confidence: 59%

Twists and the Electronic Structure of Graphitic Materials

2019

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We analyze the effect of twists on the electronic structure of configurations of infinite stacks of graphene layers. We focus on three different cases: an infinite stack where each layer is rotated with respect to the previous one by a fixed angle, two pieces of semi-infinite graphite rotated with respect to each other, and finally a single layer of graphene rotated with respect to a graphite surface. In all three cases we find a rich structure, with sharp resonances and flat bands for small twist angles. The method used can be easily generalized to more complex arrangements and stacking sequences. arXiv:1903.08403v3 [cond-mat.str-el]

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“…Below we outline in detail the fabrication procedure which was inspired by the similar method developed for suspending graphene nanostructures. [47][48][49][50][51][52][53] First, the stainless steel plate was coated with an insulating polyimide layer of 4 mm thickness. The latter was achieved by repeated, alternating steps of spin coating at 4000 rpm for 30 s and baking at 300 C for 1 hour.…”

mentioning

confidence: 99%