Neutral triplet collective mode as a decay channel in graphite

Ebrahimkhas, Morad; Jafari, S. A.

doi:10.1103/physrevb.79.205425

Cited by 11 publications

(14 citation statements)

References 36 publications

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“…However, here instead of second order equation, we obtain two set of first order equations for T ± q operators, one of which (T + q ) does not lead to split-off state for finite Ũ , while the other (T − q ) satisfying a first order equation leads to a dispersive triplet collective excitations whose energy band-width is on the scale of the hopping amplitude γ. Such a bosonic branch of excitations might be responsible for: (i) The lifetime anomaly observed in time resolved photo-emission spectroscopy of highly oriented pyrolytic graphite [24]. (ii) The kink observed in the dispersion of Dirac electrons in nearly free standing graphene samples [25].…”

Section: Summary and Discussionmentioning

confidence: 99%

Equations-of-motion method for triplet excitation operators in graphene

Jafari

Baskaran

2012

J. Phys.: Condens. Matter

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The particle-hole continuum in the Dirac sea of graphene has a unique window underneath, which in principle leaves room for bound state formation in the triplet particle-hole channel (Baskaran and Jafari 2002 Phys. Rev. Lett. 89 016402). In this work, we construct appropriate triplet particle-hole operators and, using a repulsive Hubbard-type effective interaction, we employ equations of motion to derive approximate eigenvalue equations for such triplet operators. While the secular equation for the spin density fluctuations gives rise to an equation which is second order in the strength of the short range interaction, the explicit construction of the triplet operators obtained here shows that, in terms of these operators, the second-order equation can be factorized to two first-order equations, one of which gives rise to a solution below the particle-hole continuum of Dirac electrons in undoped graphene.

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Section: Summary and Discussionmentioning

confidence: 99%

Equations-of-motion method for triplet excitation operators in graphene

Jafari

Baskaran

2012

J. Phys.: Condens. Matter

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“…This may happen in both undoped [29,30,31,32,33] and doped graphene [34]. In this work we would like to study the effect of such ladder diagrams in the electromagnetic response of graphene, and in particular to focus on the special role played by the spin-flip channel of particle-hole fluctuations.…”

Section: Introductionmentioning

confidence: 99%

Electromagnetic modes from Stoner enhancement: Graphene as a case study

Jalali-Mola

Jafari

2019

Journal of Magnetism and Magnetic Materials

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Systems with substantial spin fluctuations, can internally dress the polarization function by ladder diagram of Stoner (spin-flip) excitations. This process can drastically modify the electromagnetic response. As a case study we provide detailed analysis of the corrections to the non-local optical conductivity of both doped and undoped graphene. While the resummation of ladder diagram of Stoner excitations does not affect the TE mode in doped graphene, it allows for a new undampled TM mode in undoped graphene. This is the sole effect of corrections arising from ladder diagrams and is dominated by Stoner excitations along the ladder rung which goes away by turning off the source of spin-flip interactions.

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“…There is a widespread consensus on the large potential of graphene for electronic applications [7], [8]. The low electronic density of states near the Fermi energy and zero band-gap at neutrality point in graphene exhibit a small ON/OFF switching ratio, due to this problem the application of graphene for charge based logic devices are inhibited [9].…”

Section: Introductionmentioning

confidence: 99%

Effects of correlations on honeycomb lattice in ionic-Hubbard model

2015

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In a honeycomb lattice the symmetry has been broken by adding an ionic potential and a single-particle gap was generated in the spectrum. We have employed the iterative perturbation theory (IPT) in dynamical mean field approximation method to study the effects of competition between U and ∆ on energy gap and renormalized Fermi velocity. We found, the competition between the single-particle gap parameter and the Hubbard potential closed the energy gap and restored the semi-metallic phase, then the gap is opened again in Mott insulator phase. For a fixed ∆ by increasing U , the renormalized Fermi velocityṽ F is decreased, but change in ∆, for a fixed U , has no effects onṽ F . The difference in filling factor is calculated for various number of U, ∆. The results of this study can be implicated for gapped graphene e.g. hydrogenated graphene.

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Neutral triplet collective mode as a decay channel in graphite

Cited by 11 publications

References 36 publications

Equations-of-motion method for triplet excitation operators in graphene

Equations-of-motion method for triplet excitation operators in graphene

Electromagnetic modes from Stoner enhancement: Graphene as a case study

Effects of correlations on honeycomb lattice in ionic-Hubbard model

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