In ordinary semiconductor bilayers, exciton condensates appear at total Landau-level filling factor ${\nu }_T=1$. We predict that similar states will occur in Bernal stacked graphene bilayers at many nonzero integer filling factors. For ${\nu }_T=-3$, 1 we find that the superfluid density of the exciton condensate vanishes and that a finite-temperature fluctuation-induced first order isotropic-smectic phase transition occurs when the layer densities are not balanced. These anomalous properties of bilayer graphene exciton condensates are due to the degeneracy of Landau levels with $n=0$ and $n=1$ orbital character.

• Received 8 September 2009

DOI:https://doi.org/10.1103/PhysRevLett.104.096802