Chirality and Correlations in Graphene

Barlas, Yafis; Pereg-Barnea, T.; Polini, Marco; Asgari, Reza; MacDonald, Allan H.

doi:10.1103/physrevlett.98.236601

Cited by 215 publications

(308 citation statements)

References 31 publications

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“…[104]). When one dopes the system away from the neutrality point, screening kicks in and the electron fluid in singlelayer graphene behaves as a Fermi liquid, albeit with a number of intriguing twists [12,105,106].…”

Section: Long-range Interactionsmentioning

confidence: 99%

Artificial honeycomb lattices for electrons, atoms and photons

et al. 2013

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Artificial honeycomb lattices offer a tunable platform to study massless Dirac quasiparticles and their topological and correlated phases. Here we review recent progress in the design and fabrication of such synthetic structures focusing on nanopatterning of two-dimensional electron gases in semiconductors, molecule-by-molecule assembly by scanning probe methods, and optical trapping of ultracold atoms in crystals of light. We also discuss photonic crystals with Dirac cone dispersion and topologically protected edge states. We emphasize how the interplay between single-particle band structure engineering and cooperative effects leads to spectacular manifestations in tunneling and optical spectroscopies.

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Section: Long-range Interactionsmentioning

confidence: 99%

Artificial honeycomb lattices for electrons, atoms and photons

et al. 2013

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“…The measured frequency and weight enhancement of the in-phase optical plasmon mode follows, respectively, the square-root and the linear dependence on the number of graphene sheets in GMLS, i.e. √ N and N , which differs from the weak inlayer density dependence, n 1/4 and n 1/2 , obtained respectively for the plasmon fre- quency and its weight both in single- [25][26][27][28][29] and doublelayer [39][40][41][42] graphene structures. This effect is strikingly different from that in conventional two-dimensional systems in semiconductors where, if exchange and correlations effects 59 are neglected, the in-phase plasmon mode in a symmetrically balanced double-layer system behaves similarly to that in an individual layer with the doubled density.…”

Section: Introductionmentioning

confidence: 99%

“…The recent theoretical calculations of the bubble diagram of the Lindhard polarization function, Π 0 (ω, q), in monolayer graphene [25][26][27] show that for an arbitrary bosonic frequency, ω, and momentum, q, its dependence on the carrier density, n, is weaker, Π 0 (ω, q) ∝ √ n, than the dependence Π 0 (ω, q) ∝ n in conventional two dimensional electron systems with a parabolic energy dispersion. As a direct consequence, the frequency of charge density waves, ω p , in a quantum system of chiral massless Dirac fermions shows a unique carrier density scaling, ω p ∝ n 1/4 , which is in contrast with conventional two-dimensional plasma ω p ∝ n 1/2 .…”

Section: Introductionmentioning

confidence: 99%

“…Particularly, electron-phonon interaction phenomena have become a subject of active study in single-layer graphene structures in zero [16][17][18][19] and finite magnetic fields [20][21][22][23] . Substantial efforts have been directed towards the investigation of the linear response of doped graphene 24 and of the charge density excitations [25][26][27][28][29] and of such complex quasiparticles as plasmarons 30,31 and plasmon-phonon complexes 32 . Recently, the experimental realization of graphene double-layer structures coupled only via the Coulomb interaction [33][34][35][36][37][38] has attracted substantial theoretical interest in studying the double-layer plasmon effects [39][40][41][42] and the frictional drag 43 in two spatially separated graphene layers [44][45][46][47][48][49][50][51][52] as powerful tools for probing interaction effects of massless Dirac fermions.…”

Section: Introductionmentioning

confidence: 99%

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Plasmonic excitations in Coulomb-coupledN-layer graphene structures

2013

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We study Dirac plasmons and their damping in spatially separated N -layer graphene structures at finite doping and temperatures. The plasmon spectrum consists of one optical excitation with a square-root dispersion and N − 1 acoustical excitations with linear dispersions, which are undamped at zero temperature within a triangular energy region outside the electron-hole continuum. For any finite number of graphene layers we have found that the energy and weight of the optical plasmon increase in the long wavelength limit, respectively, as square-root and linear functions of N . This is in agreement with recent experimental findings. With an increase of the number of multilayer acoustical plasmon modes, the energy and weight of the upper lying branches also exhibit an enhancement with N . This increase is strongest for the uppermost acoustical mode so that its energy can exceed at some value of momentum the plasmon energy in an individual graphene sheet. Meanwhile, the energy of the low lying acoustical branches decreases weakly with N as compared with the single acoustical mode in double-layer graphene structures. Our numerical calculations provide a detailed understanding of the overall behavior of the wave vector dependence of the optical and acoustical multilayer plasmon modes and show how their dispersion and damping are modified as a function of temperature, interlayer spacing, and inlayer carrier density in (un)balanced graphene multilayer structures.

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“…Electronic wavefunctions in graphene systems are often described using a pseudospin language in which the spinors specify wavefunction components on different sublattices. Although the properties of graphene 2DES's can often be successfully described using an effective noninteracting electron model, studies of electron-electron interactions effects have revealed some qualitative differences compared to ordinary 2DES's 4,5 that are related to these sublattice pseudospin degrees-of-freedom.…”

Section: Introductionmentioning

confidence: 99%

Lattice theory of pseudospin ferromagnetism in bilayer graphene: Competing interaction-induced quantum Hall states

2011

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In mean-field-theory bilayer graphene's massive Dirac fermion model has a family of broken inversion symmetry ground states with charge gaps and flavor dependent spontaneous inter layer charge transfers. We use a lattice Hartree-Fock model to explore the lattice scale physics of graphene bilayers which has a strong influence on ordering energy scales and on the competition between distinct ordered states. We find that inversion symmetry is still broken in the lattice model and estimate that the transferred areal densities are ∼ 10 −5 electrons per carbon atom, that the associated energy gaps are ∼ 10 −2 eV, that the ordering condensation energies are ∼ 10 −7 eV per carbon atom, and that the differences in energy between competing ordered states are ∼ 10 −9 eV per carbon atom. We find that states with a quantized valley Hall effect are lowest in energy, but that the coupling of an external magnetic field to spontaneous orbital moments favors the broken time-reversal-symmetry states that have quantized anomalous Hall effects. Our theory predicts non monotonic behavior of the band gap at neutrality on the potential difference between layers, in qualitative agreement with recent experiments.

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Chirality and Correlations in Graphene

Cited by 215 publications

References 31 publications

Artificial honeycomb lattices for electrons, atoms and photons

Artificial honeycomb lattices for electrons, atoms and photons

Plasmonic excitations in Coulomb-coupledN-layer graphene structures

Lattice theory of pseudospin ferromagnetism in bilayer graphene: Competing interaction-induced quantum Hall states

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