Intrinsic lifetime of Dirac plasmons in graphene

We calculate the intrinsic lifetime of a Dirac plasmon in a doped graphene sheet by analyzing the role of electron-electron interactions beyond the random phase approximation. The damping mechanism at work is intrinsic since it operates also in disorder-free samples and in the absence of lattice vibrations. We demonstrate that graphene's sublattice-pseudospin degree of freedom suppresses intrinsic plasmon losses with respect to those that occur in ordinary two-dimensional electron liquids. As a byproduct, we are able to present a microscopic calculation of the homogeneous dynamical conductivity at energies below the single-particle absorption threshold.