Accurate tight-binding models for the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>π</mml:mi></mml:math>bands of bilayer graphene

Jung, Jeil; MacDonald, Allan H.

doi:10.1103/physrevb.89.035405

Cited by 145 publications

(95 citation statements)

References 74 publications

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“…In that work, the Hartree-Fock corrections to the flat bands coming from all other (∼ 150) bands were taken into account. Here, we will instead make the assumption that the effect of the Hartree-Fock contributions from the other bands is already included at some level in the model parameters which should be either fit to experiments or obtained from ab initio studies at charge neutrality [57,66]. Thus, we only include the effects arising from filling the isolated band.…”

Section: Hartree-fock Calculationmentioning

confidence: 99%

Theory of correlated insulating behaviour and spin-triplet superconductivity in twisted double bilayer graphene

et al. 2019

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Two graphene monolayers twisted by a small magic angle exhibit nearly flat bands, leading to correlated electronic states. Here we study a related but different system with reduced symmetry - twisted double bilayer graphene (TDBG), consisting of two Bernal stacked bilayer graphenes, twisted with respect to one another. Unlike the monolayer case, we show that isolated flat bands only appear on application of a vertical displacement field. We construct a phase diagram as a function of twist angle and displacement field, incorporating interactions via a Hartree-Fock approximation. At half-filling, ferromagnetic insulators are stabilized with valley Chern number . Upon doping, ferromagnetic fluctuations are argued to lead to spin-triplet superconductivity from pairing between opposite valleys. We highlight a novel orbital effect arising from in-plane fields plays an important role in interpreting experiments. Combined with recent experimental findings, our results establish TDBG as a tunable platform to realize rare phases in conventional solids.

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Section: Hartree-fock Calculationmentioning

confidence: 99%

Theory of correlated insulating behaviour and spin-triplet superconductivity in twisted double bilayer graphene

et al. 2019

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“…To extract the interlayer interaction, the full-range Wannier tight-binding hamiltonian is constructed for a 2H bilayer TMDC unit as in the monolayer case 41 . The initial orbital projections are the same atomic orbitals and the Hilbert space twice as large.…”

Section: Interlayer Pair Coupling a P-p Interlayer Couplingmentioning

confidence: 99%

Ab initio tight-binding Hamiltonian for transition metal dichalcogenides

et al. 2015

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We present an accurate ab-initio tight-binding hamiltonian for the transition-metal dichalcogenides, MoS2, MoSe2, WS2, WSe2, with a minimal basis (the d orbitals for the metal atoms and p orbitals for the chalcogen atoms) based on a transformation of the Kohn-Sham density function theory (DFT) hamiltonian to a basis of maximally localized Wannier functions (MLWF). The truncated tight-binding hamiltonian (TBH), with only on-site, first and partial second neighbor interactions, including spin-orbit coupling, provides a simple physical picture and the symmetry of the main band-structure features. Interlayer interactions between adjacent layers are modeled by transferable hopping terms between the chalcogen p orbitals. The full-range tight-binding hamiltonian (FTBH) can be reduced to hybrid-orbital k · p effective hamiltonians near the band extrema that captures important low-energy excitations. These ab-initio hamiltonians can serve as the starting point for applications to interacting many-body physics including optical transitions and Berry curvature of bands, of which we give some examples.

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“…The energy asymmetry between dimer and nondimer sites is taken into account by introducing in the final term of H an on-site energy difference = 9.6 meV between dimer sites. All these parameters are derived from the ab initio calculations [16,18].…”

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Anomalous ballistic transport in disordered bilayer graphene: A Dirac semimetal induced by dimer vacancies

Tuan

Roche

2016

Phys. Rev. B

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We report anomalous quantum transport features in bilayer graphene in the presence of a random distribution of structural vacancies. By using an efficient real-space Kubo-Greenwood transport methodology, the impact of a varying density of dimer versus nondimer vacancies is investigated in very large scale disordered models. While nondimer vacancies are shown to induce localization regimes, dimer vacancies result in an unexpected ballistic regime whose energy window surprisingly enlarges with increasing impurity density. Such counterintuitive phenomenon is explained by the formation of an effective linear dispersion in the bilayer band structure, which roots in the symmetry breaking effects driven by dimer vacancies, and provides a realization of Dirac semimetals in high dimension. DOI: 10.1103/PhysRevB.93.041403Introduction. Single layer graphene (SLG) has attracted great attention owing to its remarkable electrical, chemical, and mechanical properties providing an endless list of novel opportunities for practical applications [1]. SLG possesses a linear electronic spectrum with chiral (A-B sublattice) symmetry which leads to exotic low-energy transport such as Klein tunneling [2,3], weak antilocalization [4,5], and half-integer quantum Hall effect [6,7].Bilayer graphene (BLG) differs from SLG by the parabolic band dispersion which, however, retains the chiral nature of low-energy electronic excitations. One of the salient and unique properties of BLG is the possibility of creating an electronic band gap by applying an external gate voltage [8,9]. However surprisingly, the understanding of quantum transport in disordered BLG remains far less understood than the SLG case, because of the enhanced structural complexity. Experimental studies evidence critical differences in transport behaviors of SLG and BLG [10]. Some generalization of the localization theory in BLG has been derived [11], while a minimum conductivity σ min 4e 2 /h is predicted at the charge neutrality point (CNP) [12][13][14]. A recent scanning tunneling microscopy (STM) study shows that vacancies in graphite induce peculiar impurity states known as zero-energy modes (ZEMs) which are maximally localized at the defect position and then decay as the inverse of the distance from the vacancy [15]. The impact of ZEMs on BLG is so far poorly understood, especially the role played by dimer and nondimer vacancies which strongly differ in terms of symmetry breaking characteristics.Here, we start by analyzing the localization features of ZEMs in BLG for all types of vacancies, and found a highly inhomogeneous sublattice state population (pseudospin polarization) as reported in STM experiments [15]. The depletion of low-energy states in one sublattice is additionally further classified into two different classes depending on the vacancy position. Then by using efficient computational methods, we explore quantum transport in disordered BLG

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Accurate tight-binding models for theπbands of bilayer graphene

Cited by 145 publications

References 74 publications

Theory of correlated insulating behaviour and spin-triplet superconductivity in twisted double bilayer graphene

Theory of correlated insulating behaviour and spin-triplet superconductivity in twisted double bilayer graphene

Ab initio tight-binding Hamiltonian for transition metal dichalcogenides

Anomalous ballistic transport in disordered bilayer graphene: A Dirac semimetal induced by dimer vacancies

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