Electron–electron and electron–hole pairing in graphene structures

Lozovik, Yu. E.; Ogarkov, S. L.; Sokolik, A. A.

doi:10.1098/rsta.2010.0224

Cited by 23 publications

(38 citation statements)

References 42 publications

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“…There are nevertheless important differences, one of the most prominent ones being the lack of an intermediate energy scale between the gap and the Fermi energy which in conventional superconductivity is provided by the Debye frequency. In the present case the screened interaction crosses over as a function of frequency from the statically screened values at zero frequency to the unscreened Coulomb potential at frequencies on the order of the momentum-transfer dependent plasmon energies 11 , which vanish at large wavelengths in two-dimensional electron systems. Since the momentum transfer for scattering at the Fermi surface can take values q ∈ [0, 2k F ], the small momentum transfer region is particularly poorly described by a statically screened interaction.…”

Section: Summary and Discussionmentioning

confidence: 99%

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Interaction-enhanced coherence between two-dimensional Dirac layers

2012

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We estimate the strength of interaction-enhanced coherence between two graphene or topological insulator surface-state layers by solving imaginary-axis gap equations in the random phase approximation. Using a self-consistent treatment of dynamic screening of Coulomb interactions in the gapped phase, we show that the excitonic gap can reach values on the order of the Fermi energy at strong interactions. The gap is discontinuous as a function of interlayer separation and effective fine structure constant, revealing a first order phase transition between effectively incoherent and interlayer coherent phases. To achieve the regime of strong coherence the interlayer separation must be smaller than the Fermi wavelength, and the extrinsic screening of the medium embedding the Dirac layers must be negligible. In the case of a graphene double-layer we comment on the supportive role of the remote π-bands neglected in the two-band Dirac model.

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Section: Summary and Discussionmentioning

confidence: 99%

“…This problem has been studied previously using a variety of approaches and approximations [7][8][9][10][11] . To our knowledge only one study has accounted for the dynamic nature of screening 11 , and none have accounted simultaneously for the reduction of screening 12 that accompanies the appearance of an interlayer coherence gap.…”

Section: Introductionmentioning

confidence: 99%

Interaction-enhanced coherence between two-dimensional Dirac layers

2012

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“…24-33. It was shown that both weak and strong coupling regimes of the pairing are achievable experimentally. 24 Estimates of the critical temperature T c at strong coupling [25][26][27][28][29][30] are very dependent on the model and approximations used, ranging from room temperature, with the unscreened Coulomb attraction taken as a pairing potential, 25,26 to unobservably small values given by Bardeen-Cooper-Shrieffer (BCS) theory with screened interaction. 27 The pairing in a graphene bilayer at strong coupling was argued 28,29,33 to involve both conduction and valence bands of electrons and holes, i.e., it is multiband.…”

Section: Introductionmentioning

confidence: 99%

“…27 A study of the problem, taking into account the effects of the frequency dependence of the gap and the pairing potential, was presented in Ref. 30.…”

Section: Introductionmentioning

confidence: 99%

Condensation of electron-hole pairs in a two-layer graphene system: Correlation effects

2012

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Condensation of pairs formed by spatially separated electrons and holes in a system of two isolated graphene layers is studied beyond the mean-field approximation. Suppression of the screening of the pairing interaction at large distances, caused by the appearance of the gap, is considered self-consistently. A mutual positive feedback between the appearance of the gap and the enlargement of the interaction leads to a sharp transition to a correlated state with a greatly increased gap above some critical value of the coupling strength. At a coupling strength below the critical value, this correlation effect increases the gap approximately by a factor of 2. The maximal coupling strength achievable in experiments is close to the critical value. This indicates the importance of correlation effects in closely spaced graphene bilayers at weak substrate dielectric screening. Another effect beyond the mean-field approximation considered is the influence of vertex corrections on the pairing, which is shown to be very weak.

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“…Meanwhile, in the electronic bilayer systems, those mentioned phase transitions are indistinguishable as it was shown in references [12,21]. On the other hand, the inclusion of the dynamic screening and the full band structure favors the pairing and condensation [25][26][27].…”

Section: Introductionmentioning

confidence: 76%

Density of states in the bilayer graphene with the excitonic pairing interaction

Apinyan

Kopeć

2017

Eur. Phys. J. B

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Abstract. In the present paper, we consider the excitonic effects on the single particle normal density of states (DOS) in the bilayer graphene (BLG). The local interlayer Coulomb interaction is considered between the particles on the non-equivalent sublattice sites in different layers of the BLG. We show the presence of the excitonic shift of the neutrality point, even for the noninteracting layers. Furthermore, for the interacting layers, a very large asymmetry in the DOS structure is shown between the particle and hole channels. At the large values of the interlayer hopping amplitude, a large number of DOS at the Dirac's point indicates the existence of the strong excitonic coherence effects between the layers in the BLG and the enhancement of the excitonic condensation. We have found different competing orders in the interacting BLG. Particularly, a phase transition from the hybridized excitonic insulator phase to the coherent condensate state is shown at the small values of the local interlayer Coulomb interaction.

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Electron–electron and electron–hole pairing in graphene structures

Cited by 23 publications

References 42 publications

Interaction-enhanced coherence between two-dimensional Dirac layers

Interaction-enhanced coherence between two-dimensional Dirac layers

Condensation of electron-hole pairs in a two-layer graphene system: Correlation effects

Density of states in the bilayer graphene with the excitonic pairing interaction

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