Dynamical Screening and Excitonic Instability in Bilayer Graphene
Dynamical Screening and Excitonic Instability in Bilayer Graphene
Electron interactions in undoped bilayer graphene lead to an instability of the gapless state, "which-layer" symmetry breaking, and energy gap opening at the Dirac point. In contrast with single-layer graphene, the bilayer system exhibits instability even for an arbitrarily weak interaction. A controlled theory of this instability for realistic dynamically …