Tunable strongly coupled superconductivity in magic-angle twisted trilayer graphene

Park, Jeong Min; Cao, Yuan; Watanabe, Kenji; Taniguchi, Takashi; Jarillo‐Herrero, Pablo

doi:10.1038/s41586-021-03192-0

Cited by 588 publications

(506 citation statements)

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“…This was very recently confirmed, and it was found that at an average angle of ±1.56°, twisted trilayer graphene exhibited extraordinary superconductive properties and considering its low charge density, it had the strongest electron pairing ever observed [14]. tTLG was noted As superior to bilayer graphene because it was superconductive at a higher temperature and had better tunability in terms of its electronic structure and superconducting characteristics than bilayer graphene [15]. The electrical properties of tTLG are already well established, however, there is a research gap concerning the mechanical behavior of this material [16][17][18].…”

Section: Introductionmentioning

confidence: 73%

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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Section: Introductionmentioning

confidence: 73%

Atomic Insights into Fracture Characteristics of Twisted Tri-Layer Graphene

2021

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“…Yet, superconductivity has been found in a growing number of materials in such strong-coupling regime. Two famous examples are (i) strontium titanate, the most dilute bulk superconductor with Fermi energy as small as 1 meV (6), and (ii) magic-angle graphene with a record-low density n 2D ∼ 10 11 cm −2 and a very small bandwidth of ∼10 meV (7)(8)(9)(10). The ratio of superconducting transition temperature T c and Fermi temperature E F /k B far exceeds typical values, reaching as high as 0.01 in strontium titanate (6) and 0.1 in magic-angle graphene (8).…”

Section: Introductionmentioning

confidence: 99%

New mechanism and exact theory of superconductivity from strong repulsive interaction

Crépel

2021

Sci. Adv.

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We introduce a general mechanism for superconductivity in Fermi systems with strong repulsive interaction. Because kinetic terms are small compared to the bare repulsion, the dynamics of charge carriers is constrained by the presence of other nearby carriers. By treating kinetic terms as a perturbation around the atomic limit, we show that pairing can be induced by correlated multiparticle tunneling processes that favor two itinerant carriers to be close together. Our analytically controlled theory provides a quantitative formula relating Tc to microscopic parameters, with maximum Tc reaching about 10% of the Fermi temperature. Our work demonstrates a powerful method for studying strong coupling superconductivity with unconventional pairing symmetry. It also offers a realistic new route to realizing finite angular momentum superfluidity of spin-polarized fermions in optical lattice.

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“…These twisted bilayer graphene (TBG) superlattices represent versatile two-dimensional (2D) materials in which depend on the rotation angle, θ , and change carrier doping, n , a wide number of physical effects, including superconductivity, can emerge [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. It should be noted that recently Park et al [ 16 ] experimentally found that magic-angle twisted trilayer graphene (MATTBG) superlattices also have correlated electronic states similarly to the ones observed in their bilayer counterparts.…”

Section: Introductionmentioning

confidence: 96%

“…One of the most important problem in understanding of all TBGs is the mechanism of the charge carrier interaction, where some research groups proposed that there is a dominant role of the electron–phonon interaction (which is also considered as the emerging mechanism for the superconductivity in MATBG by several research groups [ 17 , 18 , 19 , 20 , 21 , 22 ]), while the other groups showed evidence for the prevalence of the electron–electron interaction [ 3 , 10 , 16 , 23 ], and recently, new experiments demonstrated the dominance of the electron–magnon interaction [ 6 , 9 , 24 , 25 ]. It should be noted that Kerelsky et al [ 26 ] reported that the superconducting state in TBG emerges at the same doping levels, n , and the twist angles, θ , at which the electron–electron interaction reaches its maximal values.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the Charge Carrier Interaction in Metallic Twisted Bilayer Graphene Superlattices

Talantsev

2021

Nanomaterials

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The mechanism of charge carrier interaction in twisted bilayer graphene (TBG) remains an unresolved problem, where some researchers proposed the dominance of the electron–phonon interaction, while the others showed evidence for electron–electron or electron–magnon interactions. Here we propose to resolve this problem by generalizing the Bloch–Grüneisen equation and using it for the analysis of the temperature dependent resistivity in TBG. It is a well-established theoretical result that the Bloch–Grüneisen equation power-law exponent, p, exhibits exact integer values for certain mechanisms. For instance, p = 5 implies the electron–phonon interaction, p = 3 is associated with the electron–magnon interaction and p = 2 applies to the electron–electron interaction. Here we interpret the linear temperature-dependent resistance, widely observed in TBG, as p→1, which implies the quasielastic charge interaction with acoustic phonons. Thus, we fitted TBG resistance curves to the Bloch–Grüneisen equation, where we propose that p is a free-fitting parameter. We found that TBGs have a smoothly varied p-value (ranging from 1.4 to 4.4) depending on the Moiré superlattice constant, λ, or the charge carrier concentration, n. This implies that different mechanisms of the charge carrier interaction in TBG superlattices smoothly transition from one mechanism to another depending on, at least, λ and n. The proposed generalized Bloch–Grüneisen equation is applicable to a wide range of disciplines, including superconductivity and geology.

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Tunable strongly coupled superconductivity in magic-angle twisted trilayer graphene

Cited by 588 publications

References 44 publications

Atomic Insights into Fracture Characteristics of Twisted Tri-Layer Graphene

Atomic Insights into Fracture Characteristics of Twisted Tri-Layer Graphene

New mechanism and exact theory of superconductivity from strong repulsive interaction

Quantifying the Charge Carrier Interaction in Metallic Twisted Bilayer Graphene Superlattices

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