Interaction effects and superconductivity signatures in twisted double-bilayer WSe<sub>2</sub>

An, Liheng; Cai, Xiangbin; Pei, Ding; Huang, Meizhen; Wu, Zefei; Zhou, Zishu; Lin, Jiangxiazi; Ying, Zhenhan; Ye, Ziqing; Feng, Xuemeng; Gao, Ruiyan; Cacho, Céphise; Watson, M. D.; Chen, Yulin; Wang, Ning

doi:10.1039/d0nh00248h

Cited by 91 publications

(72 citation statements)

References 33 publications

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“…Two-dimensional (2D) van der Waals heterostructures with an interlayer twist have provided a new avenue for observing emergent tunable many-body electron phenomena. Recent experimental realizations include twisted bilayer graphene (tBG) near the so-called “magic angle” of 1.1° ( 1 – 3 ), twisted double-bilayer graphene (tDBG) ( 4 – 6 ), ABC trilayer graphene on near-perfectly aligned hexagonal boron nitride (hBN) (ABC-tLG/hBN) ( 7 , 8 ) and transition-metal dichalcogenide heterostructures ( 9 – 12 ) [with predictions on a variety of other systems ( 13 , 14 )]. All of these systems host an interplay of two phenomena––the presence of one or more van Hove singularities (which we colloquially refer to as “flat bands” henceforth) at low energy where the density of states is sharply peaked, and the existence of a moiré pattern that creates a unit cell that is about a hundred times larger than the carbon–carbon nearest-neighbor distance in graphene.…”

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confidence: 99%

“…The large number of electrons with quenched kinetic energy make the flat bands conducive to interaction-driven phases ( 15 ). The enlarged moiré unit cell is thought to reduce both the flat-band bandwidth and the interaction energy scales, and also introduces easily accessible integer fillings that create Mott-like insulating states ( 1 – 12 ), the relation of which to nearby superconductivity is debated. A natural question that arises from all of these works is whether the moiré pattern is a necessary condition for the observation of correlated many-body phases, or whether it is simply sufficient to further reduce the flat-band bandwidth and hence the kinetic energy in the heterostructure.…”

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confidence: 99%

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Moiréless correlations in ABCA graphene

Kerelsky

Rubio-Verdú

Xian

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

104

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Atomically thin van der Waals materials stacked with an interlayer twist have proven to be an excellent platform toward achieving gate-tunable correlated phenomena linked to the formation of flat electronic bands. In this work we demonstrate the formation of emergent correlated phases in multilayer rhombohedral graphene––a simple material that also exhibits a flat electronic band edge but without the need of having a moiré superlattice induced by twisted van der Waals layers. We show that two layers of bilayer graphene that are twisted by an arbitrary tiny angle host large (micrometer-scale) regions of uniform rhombohedral four-layer (ABCA) graphene that can be independently studied. Scanning tunneling spectroscopy reveals that ABCA graphene hosts an unprecedentedly sharp van Hove singularity of 3–5-meV half-width. We demonstrate that when this van Hove singularity straddles the Fermi level, a correlated many-body gap emerges with peak-to-peak value of 9.5 meV at charge neutrality. Mean-field theoretical calculations for model with short-ranged interactions indicate that two primary candidates for the appearance of this broken symmetry state are a charge-transfer excitonic insulator and a ferrimagnet. Finally, we show that ABCA graphene hosts surface topological helical edge states at natural interfaces with ABAB graphene which can be turned on and off with gate voltage, implying that small-angle twisted double-bilayer graphene is an ideal programmable topological quantum material.

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confidence: 99%

mentioning

confidence: 99%

Moiréless correlations in ABCA graphene

Kerelsky

Rubio-Verdú

Xian

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

104

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“…The discovery of superconductivity in twisted bilayer graphene was groundbreaking in the field of material science and was followed by a sudden rise in research concerning twistronic materials [7][8][9][10][11]. The scope of this discovery also extended to other Moirépatterned 2D materials that exhibit superconductivity, such as twisted bilayer tungsten diselenide (WSe 2 ) and boron nitride (BN) between layers of graphene [12,13].…”

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confidence: 99%

Atomic Insights into Fracture Characteristics of Twisted Tri-Layer Graphene

2021

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Graphene twistronics have recently gained significant attention due their superconductive behavior as a consequence of their tunable electronic properties. Although the electronic properties of twisted graphene have been extensively studied, the mechanical properties and integrity of twisted trilayer graphene (tTLG) under loading is still elusive. We investigated the fracture mechanics of tTLG with a twist angle of ±1.53° utilizing molecular dynamics simulation. This twist angle was chosen because it is known to exhibit highly superconductive behavior. The results indicate that tTLG does not preserve the excellent mechanical properties typically associated with graphene, with toughness and fracture strain values much lower in comparison. The Young’s modulus was an exception with values relatively close to pristine graphene, whereas the tensile strength was found to be roughly half of the intrinsic strength of graphene. The fracture toughness, fracture strain and strength converge as the crack length increases, reaching 0.26 J/m3, 0.0217 and 39.9 GPa at a crack length of 8 nm, respectively. The Griffth critical strain energy is 19.98 J/m2 and the critical stress intensity factor Kc is 4.47 MPa M1/2, in good agreement with that of monolayer graphene in the experiment. Our atomic insights might be helpful in the material design of twisted trilayer graphene-based electronics.

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“…TBG has also motivated the design of twisted structures of other van der Waals materials. 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 In contrast, chirality-induced transport phenomena are less explored thus far. 29 , 30 , 31 , 32…”

Section: Introductionmentioning

confidence: 99%

Chirality-Induced Giant Unidirectional Magnetoresistance in Twisted Bilayer Graphene

2021

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Summary Twisted bilayer graphene (TBG) exhibits fascinating correlation-driven phenomena like the superconductivity and Mott insulating state, with flat bands and a chiral lattice structure. We find by quantum-transport calculations that the chirality leads to a giant unidirectional magnetoresistance (UMR) in TBG, where the unidirectionality refers to the resistance change under the reversal of the direction of current or magnetic field. We point out that flat bands significantly enhance this effect. The UMR increases quickly upon reducing the twist angle, and reaches about 20% for an angle of 1.5° in a 10 T in-plane magnetic field. We propose the band structure topology (asymmetry), which leads to a direction-sensitive mean free path, as a useful way to anticipate the UMR effect. The UMR provides a probe for chirality and band flatness in the twisted bilayers.

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Interaction effects and superconductivity signatures in twisted double-bilayer WSe₂

Abstract: Twisted bilayer graphene provides a new two-dimensional platform for studying electron interaction phenomena and flat band properties such as correlated insulator transition, superconductivity and ferromagnetism at certain magic angles. Here,...

Cited by 91 publications

References 33 publications

Moiréless correlations in ABCA graphene

Moiréless correlations in ABCA graphene

Atomic Insights into Fracture Characteristics of Twisted Tri-Layer Graphene

Chirality-Induced Giant Unidirectional Magnetoresistance in Twisted Bilayer Graphene

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Interaction effects and superconductivity signatures in twisted double-bilayer WSe2

Abstract: Twisted bilayer graphene provides a new two-dimensional platform for studying electron interaction phenomena and flat band properties such as correlated insulator transition, superconductivity and ferromagnetism at certain magic angles. Here,...

Cited by 91 publications

References 33 publications

Moiréless correlations in ABCA graphene

Moiréless correlations in ABCA graphene

Atomic Insights into Fracture Characteristics of Twisted Tri-Layer Graphene

Chirality-Induced Giant Unidirectional Magnetoresistance in Twisted Bilayer Graphene

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Product

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Interaction effects and superconductivity signatures in twisted double-bilayer WSe₂