Impact of disorder on Dirac plasmon losses

Recent scattering-type scanning near-field optical spectroscopy (s-SNOM) experiments on single-layer graphene have reported Dirac plasmon lifetimes that are substantially shorter than the dc transport scattering time tau(tr). We argue that this discrepancy arises from the fact that the plasmon lifetime is fundamentally different from tau(tr) since it is controlled by the imaginary part of the current-current linear response function at finite momentum and frequency. Taking this into account, we show that a minimal theory of the extrinsic lifetime of Dirac plasmons due to scattering against charged impurities yields a plasmon damping rate which is in good agreement with s-SNOM experimental results.