Density fluctuation effects on the exciton condensate in double-layer graphene

We describe the robustness of an excitonic condensate in double-layer graphene against layer density fluctuations and the associated charge inhomogeneity, and discuss the implications for observing the condensate in current experimental conditions. We solve the mean-field equations for a finite imbalance in the Fermi energies in each layer and utilize the results in two phenomenological models for inhomogeneity. We find that the stability of the excitonic condensate against density fluctuations is strongly dependent on the size of the excitonic gap, and that transport experiments (such as Coulomb drag) are promising methods for observing the condensate.