Loss mechanisms in graphene plasmonics*

``Dirac'' plasmons are self-sustained carrier density oscillations that occur in a doped graphene sheet. These collective modes have recently attracted enormous experimental and theoretical interest for their potential use in plasmonics [1]. In this talk I will discuss the two most important figures of merit of ``graphene plasmonics,'' namely the ratio between the Dirac plasmon wavelength and the illumination wavelength, and the Dirac plasmon damping rate. I will emphasize the subtle difference between plasmon lifetime and Drude transport scattering time. I will then present a theoretical framework that enables fully microscopic calculations of Dirac plasmon damping rates due to electron-electron [2], electron-impurity [3], and electron-phonon [4] collisions. Finally, I will conclude by discussing how our theoretical predictions compare with recent accurate measurements [5] in high-quality graphene sheets encapsulated in boron nitride.\\[4pt] Work done in collaboration with A. Principi, M. Carrega, G. Vignale, A. Woessner, M.B. Lundeberg, Y. Gao, P. Alonso-Gonz\'{a}lez, K. Watanabe, T. Taniguchi, J. Hone, R. Hillenbrand, and F.H.L. Koppens. \\[4pt] [1] A.N. Grigorenko, M. Polini, and K.S. Novoselov, Nature Photon. \textbf{6}, 749 (2012).\\[0pt] [2] A. Principi, G. Vignale, M. Carrega, and M. Polini, Phys. Rev. B \textbf{88}, 195405 (2013).\\[0pt] [3] A. Principi, G. Vignale, M. Carrega, and M. Polini, Phys. Rev. B \textbf{88}, 121405(R) (2013).\\[0pt] [4] A. Principi, M. Carrega, M.B. Lundeberg, A. Woessner, F.H.L. Koppens, G. Vignale, and M. Polini, Phys. Rev. B \textbf{90}, 165408 (2014).\\[0pt] [5] A. Woessner, M.B. Lundeberg, Y. Gao, A. Principi, P. Alonso-Gonz\'{a}lez, M. Carrega, K. Watanabe, T. Taniguchi, G. Vignale, M. Polini, J. Hone, R. Hillenbrand, and F.H.L. Koppens, Nature Mater. (in press) and arXiv:1409.5674.