Interaction-Enhanced Coherence Between Two-Dimensional Dirac Layers

Abstract

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 $\pi$-bands neglected in the two-band Dirac model.

14 pages, 9 figures

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Cited by in corpus (6)

• Cooper pairing of electrons and holes in graphene bilayer: Correlation effects
• Gapped phase in AA stacked bilayer graphene
• Odd momentum pairing and superconductivity in vertical graphene heterostructures
• Density fluctuation effects on the exciton condensate in double layer graphene
• Photoemission spectra of massless Dirac fermions on the verge of exciton condensation
• Phases of the excitonic condensate in two-layer graphene