Interaction-enhanced coherence between two-dimensional Dirac layers

Inti Sodemann, D. A. Pesin, and A. H. MacDonald
Phys. Rev. B 85, 195136 – Published 22 May 2012

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 π bands neglected in the two-band Dirac model.

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  • Received 15 March 2012

DOI:https://doi.org/10.1103/PhysRevB.85.195136

©2012 American Physical Society

Authors & Affiliations

Inti Sodemann1,2, D. A. Pesin1, and A. H. MacDonald1

  • 1Department of Physics, University of Texas at Austin, Austin, Texas 78712, USA
  • 2Kavli Institute for Theoretical Physics, Santa Barbara, California 93106, USA

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Issue

Vol. 85, Iss. 19 — 15 May 2012

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