  Exciton condensation, a Bose-Einstein-like condensation of excitons, was
recently reported in an electronic double layer (EDL) of graphene. We show that
a universal quantum signature for exciton condensation can be used to both
identity and quantify exciton condensation in molecular systems from direct
calculations of the two-electron reduced density matrix. Computed large
eigenvalues in the particle-hole reduced-density matrices of pentacene and
hexacene EDLs reveal the beginnings of condensation, suggesting the potential
for exciton condensation in smaller scale molecular EDLs.
