Effect of interlayer bare tunneling on electron-hole coherence in graphene bilayers

Abstract

The influence of single-particle interlayer coupling on the many-body electron-hole condensation between two graphene monolayers separated by a thin dielectric film is studied. This work extends prior work by treating interlayer coupling, which controls critical interlayer tunneling currents, nonperturbatively. As before, a \ensuremath{\pi}-band tight-binding model of the graphene bilayer is combined with Fock mean-field theory. Our results demonstrate that both the strength and the sublattice distribution of interlayer coupling play essential roles. We consider both Bernal-like and quasi-hexagonal forms, and self-consistently solve for the condensate. We find that stronger bare coupling can considerably affect the nature of the condensate state itself, selecting a preferred pattern of interlayer coherence among the atomic sublattices. When this occurs, the sensitivity of the critical current to the nature of the bare coupling decreases substantially. Because condensate control via gated charge imbalance has been proposed for beyond Complementary Metal-Oxide Semiconductor (CMOS) switching, we also examine the effect of increasing charge imbalance between layers on the condensate strength as well as the critical current.