Electronic band structure and pinning of Fermi energy to van Hove singularities in twisted bilayer graphene: a self consistent approach

Cea, Tommaso; Walet, Niels R.; Guinea, Francisco

doi:10.48550/arxiv.1906.10570

Cited by 4 publications

(4 citation statements)

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“…As we assume the Hartree potential preserves all symmetries, V H can be written as Fourier series similar to Eq. ( 2), and the Coulomb interaction only renormalizes the band structure [21,22]. In Fig.…”

Section: Turementioning

confidence: 97%

Moiré quantum chemistry: charge transfer in transition metal dichalcogenide superlattices

Zhang,

Yuan,

2019

Preprint

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Transition metal dichalcogenide (TMD) bilayers have recently emerged as a robust and tunable moiré system for studying and designing correlated electron physics. In this work, we provide an electronic structure theory that maps long-period heterobilayer TMD superlattices to diatomic crystals with cations and anions. We find the interplay between moiré potential and Coulomb interaction leads to filling-dependent charge transfer between AA and AB stacking regions several nanometers apart. We show the insulating state at half filling found in recent experiments on WSe2/WS2 is a charge-transfer insulator rather than a Mott-Hubbard insulator. Our work reveals the richness of simplicity in moiré quantum chemistry.

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Section: Turementioning

confidence: 97%

Moiré quantum chemistry: charge transfer in transition metal dichalcogenide superlattices

Zhang,

Yuan,

2019

Preprint

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“…The intense interest arises mainly from the new physics brought in by the low-lying flat bands near magic angles in tBLG [5]. The average Coulomb interaction [6,7] between the quasiparticles in narrow bands is far larger than the kinetic energy, giving access to a strongly correlated regime and providing an ideal system for the observation of collective many-body phenomena.…”

Section: Introductionmentioning

confidence: 99%

Enhanced hydrodynamic transport in near magic angle twisted bilayer graphene

et al. 2020

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Using the semiclassical quantum Boltzmann theory and employing the Dirac model with twist angle-dependent Fermi velocity we obtain results for the electrical resistivity, the electronic thermal resistivity, the Seebeck coefficient, and the Wiedemann-Franz ratio in near magic angle twisted bilayer graphene, as functions of doping density (around the charge-neutrality-point) and modified Fermi velocityṽ. Theṽ-dependence of the relevant scattering mechanisms, i.e. electron-hole Coulomb, long-ranged impurities, and acoustic gauge phonons, is considered in detail. We find a range of twist angles and temperatures, where the combined effect of momentum-non-conserving collisions (long-ranged impurities and phonons) is minimal, opening a window for the observation of strong hydrodynamic transport. Several experimental signatures are identified, such as a sharp dependence of the electric resistivity on doping density and a large enhancement of the Wiedeman-Franz ratio and the Seebeck coefficient.

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“…In this Letter, we predict that the insulator in twisted TMD at half filling is an excitonic spin density wave formed by the pairing of electrons and holes in minibands at different valleys. This electron-hole pairing is strongly enhanced by a van Hove singularity [13][14][15][16][17][18][19][20] (VHS) near the Fermi level. We show that the detuning of the displacement field has a pair breaking effect on the excitonic insulator, while the Zeeman coupling to an outof-plane magnetic field is non-pair-breaking at leading order.…”

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confidence: 99%

Excitonic density wave and spin-valley superfluid in bilayer transition metal dichalcogenide

2019

Preprint

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Recently, twisted bilayer WSe2[1] emerged as a new robust moiré system hosting a correlated insulator at moiré half-filling over a range of twist angle and displacement field. In this work, we present a theory of this insulating state as an excitonic density wave due to intervalley electronhole pairing. We show that exciton condensation is strongly enhanced by a van Hove singularity near the Fermi level. Our theory explains the remarkable sensitivity of the insulating state to the displacement field as well as the lack thereof to the Zeeman field in terms of pair-breaking versus non-pair-breaking perturbations. We further predict superfluid spin transport in this electrical insulator, which can be detected by optical spin injection and spatial-temporal imaging.

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Electronic band structure and pinning of Fermi energy to van Hove singularities in twisted bilayer graphene: a self consistent approach

Cited by 4 publications

References 0 publications

Moiré quantum chemistry: charge transfer in transition metal dichalcogenide superlattices

Moiré quantum chemistry: charge transfer in transition metal dichalcogenide superlattices

Enhanced hydrodynamic transport in near magic angle twisted bilayer graphene

Excitonic density wave and spin-valley superfluid in bilayer transition metal dichalcogenide

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