Signatures of tunable superconductivity in a trilayer graphene moiré superlattice

Chen, Guorui; Sharpe, Aaron; Gallagher, Patrick; Rosen, Ilan T.; Fox, Eli; Jiang, Lili; Lyu, Bosai; Li, Hongyuan; Watanabe, Kenji; Taniguchi, Takashi; Jung, Jeil; Shi, Zhiwen; Goldhaber‐Gordon, David; Zhang, Yuanbo; Wang, Feng

doi:10.1038/s41586-019-1393-y

Cited by 638 publications

(448 citation statements)

References 38 publications

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“…With irrelevant perturbations only, the critical point at p = 0 is not affected, since irrelevant perturbations become negligible when arrpoaching p = 0. As a result, the total DOS is asymptotically power-law divergent (19) as ε → 0, up to a non-singular background contribution [13].…”

Section: E Perturbationmentioning

confidence: 99%

“…Recent experimental progress in 2D moiré superlattices such as twisted bilayer graphene [14][15][16][17] and graphene heterostructures [18][19][20][21] has enabled us to continuously tune electronic band structures in 2D systems, where high-order VHS can be realized at symmetric points [13] or generic positions [22], and could be relevant to experimentally observed insulating and superconducting phases at magic angle [14][15][16].…”

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confidence: 99%

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Classification of critical points in energy bands based on topology, scaling, and symmetry

Yuan

2020

Phys. Rev. B

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A critical point of the energy dispersion is the momentum where electron velocity vanishes. At the corresponding energy, the density of states (DOS) exhibits non-analyticity such as divergence. Critical points can be first classified as ordinary and high-order ones, and the ordinary critical points have been studied thoroughly by Léon van Hove. In this work, we describe and classify high-order critical points based on topology, scaling and symmetry, which are beyond Léon van Hove's framework. We show that high-order critical points can have power-law divergent DOS with particle-hole asymmetry, and can be realized at generic or symmetric momenta by tuning a few parameters such as twist angle, strain, pressure and/or external fields.

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Section: E Perturbationmentioning

confidence: 99%

mentioning

confidence: 99%

Classification of critical points in energy bands based on topology, scaling, and symmetry

Yuan

2020

Phys. Rev. B

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“…Consider a simplified but highly informative toy model: a twodimensional (2D) electron gas in a periodic potential of periodicity L. The periodic potential leads to the formation of a set of minibands in the electron bandstructure. The on-site Coulomb potential U and the electronic bandwidth W of the lowest electronic miniband can be estimated as ~2 4 and ~ℏ 2 2 2 * ~ℏ 2 2 2 * 2 , and the ratio U/W scales linearly with me*L. Here is the effective dielectric constant, and me* is the electron effective mass. Strong correlation (with U/W > 1) can be readily achieved with sufficiently large me*L: for example, with a moiré superlattice (L ~ 10 nm) and an effective mass me* > 0.1m0 for ε ~ 4ε0.…”

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confidence: 99%

Mott and generalized Wigner crystal states in WSe2/WS2 moiré superlattices

Regan¹,

Wang²,

Choi³

et al. 2020

Nature

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787

532

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Moiré superlattices are emerging as a new route for engineering strongly correlated electronic states in two-dimensional van der Waals heterostructures, as recently demonstrated in the correlated insulating and superconducting states in magic-angle twisted bilayer graphene and ABC trilayer graphene/boron nitride moiré superlattices 1-4 . Transition metal dichalcogenide (TMDC) moiré heterostructures provide another exciting model system to explore correlated quantum phenomena 5 , with the addition of strong light-matter interactions and large spin-orbital coupling. Here we report the optical detection of strongly correlated phases in semiconducting WSe2/WS2 moiré superlattices. Our sensitive optical detection technique reveals a Mott insulator state at one hole per superlattice site (ν = 1), and surprising insulating phases at fractional filling factors ν = 1/3 and 2/3, which we assign to generalized Wigner crystallization on an underlying lattice 6-9 . Furthermore, the unique spin-valley optical selection rules 10-12 of TMDC heterostructures allow us to optically create and investigate low-energy spin excited states in the Mott insulator. We reveal an especially slow spin relaxation lifetime of many microseconds in the Mott insulating state, orders-of-magnitude longer than that of charge excitations. Our studies highlight novel correlated physics that can emerge in moiré superlattices beyond graphene.

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“…A related platform for studying correlated physics is the Moiré superlattice formed when trilayer graphene is aligned with boron nitride. Unlike magic angle twisted bilayer graphene, the bandwidth and the topology of the minibands can be controlled by the strength of the applied displacement field resulting in gate-tunable Mott insulating and superconducting states [13,14]. Also in this case, a correlated ferromagnetic Chern insulator has been reported at a filling corresponding to one hole per Moiré unit cell [15].…”

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confidence: 99%

Particle-Hole Duality, Emergent Fermi Liquids, and Fractional Chern Insulators in Moiré Flatbands

2020

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Moiré flatbands, occurring e.g. in twisted bilayer graphene at magic angles, have attracted ample interest due to their high degree of experimental tunability and the intriguing possibility of generating novel strongly interacting phases. Here we consider the core problem of Coulomb interactions within fractionally filled spin and valley polarized Moiré flatbands and demonstrate that the dual description in terms of holes, which acquire a non-trivial hole-dispersion, provides key physical intuition and enables the use of standard perturbative techniques for this strongly correlated problem. In experimentally relevant examples such as ABC stacked trilayer and twisted bilayer graphene aligned with boron nitride, it leads to emergent interaction-driven Fermi liquid states at electronic filling fractions down to around 1/3 and 2/3 respectively. At even lower filling fractions, the electron density still faithfully tracks the single-hole dispersion while exhibiting distinct non-Fermi liquid behavior. Most saliently, we provide microscopic evidence that high temperature fractional Chern insulators can form in twisted bilayer graphene aligned with hexagonal boron nitride.Setup. Motived by the recent discoveries [11][12][13]15] along with theoretical predictions [16,21] of spin and valley polarized insulators at integer fillings in various Moiré bands, we consider electrons with polarized spin arXiv:1912.04907v1 [cond-mat.mes-hall]

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Signatures of tunable superconductivity in a trilayer graphene moiré superlattice

Cited by 638 publications

References 38 publications

Classification of critical points in energy bands based on topology, scaling, and symmetry

Classification of critical points in energy bands based on topology, scaling, and symmetry

Mott and generalized Wigner crystal states in WSe2/WS2 moiré superlattices

Particle-Hole Duality, Emergent Fermi Liquids, and Fractional Chern Insulators in Moiré Flatbands

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