paper

Dynamical Screening and Ferroelectric-type Excitonic Instability in Bilayer Graphene

arXiv:0907.5395 · doi:10.1103/PhysRevLett.104.156803

Abstract

Electron interactions in undoped bilayer graphene lead to instability of the gapless state, `which-layer' symmetry breaking, and energy gap opening at the Dirac point. In contrast to single layer graphene, the bilayer system exhibits instability even for arbitrarily weak interaction. A controlled theory of this instability for realistic dynamically screened Coulomb interactions is developed, with full acount of dynamically generated ultraviolet cutoff. This leads to an energy gap that scales as a power law of the interaction strength, making the excitonic instability readily observable.

4 pgs, 2 fgs

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