Momentum dependence and losses in graphene plasmons Graphene Nanophotonics Benasque, 2013, Mar 03 -- Mar 08 Outline Damping mechanisms Plasmons in ribbons Experimental results Mid-infrared plasmons in scaled graphene nanostructures H. Yan, T. Low, W. Zhu, Y. Wu, M. Freitag, X. Li, F. G., P. Avouris, F. Xia arXiv:1209.1984, Nature Photonics, in press L. Martín-Moreno, A. Nikitin, F. García-Vidal, M. M. Fogler Damping mechanisms Higher order processes, multiple electron-hole pairs Lack of momentum conservation Decay into other excitations: phonons, … Elastic scattering j e 2 vF k F i k j 2 k k k+q k’ vF elastic mean free path k p q i 2 e 2vF k F q 2 Finite systems vF D D Inhomogeneous electric fields T. Low, M. M. Fogler, F. G, unpublished Edges Local excitations p(q) 4 q 4 L-1 Inhomogeneous electric fields F r , t 0 e q y Non local conductivity, clean system 2 kF q vF Im q, vF2 q 0 q vF e2 q, Im q, 2 q 1ms, EF=0.4eV E t p E 1 A d q F q 2 2 d q F q q, 1 F A 2 2 2 vF3 q 3p 2 vF2 q 2p e2kF 1 D2 Surface polar modes H e sp M sp 2 1 M sp ak q ak bq bq A pq e 2 e 2 q z 2 F env q 0 sp 1 1 F 2 env 0 env 2 pl2 q sp2 * env 1 2 2 2 2 i i sp sp sp * 4 sp2 * sp F 2 Si O2 has polar modes which induce long range electrostatic potentials. The dielectric constant of the system is modified. Optical phonons q k’ k k+q Optical phonons at G, ph0.2 eV Coupling through changes in bond lengths Weak dispersion H e ph t a u x iu y a t 23 t a 0 1/ u x iu y 1 t j u 0 vF a 2 t D F ph a M ph 1 Experiments Y. Yan, T. Low, W. Zhu,Y. Wu, M. Freitag, X. Li, F. G., P. Avouris, and F. Xia, arXiv:1209.1984, Nature Phys., in press Nanoribbons, antidots , and nanodisks defined by electron beam litography. The samples lie on CVD graphene on SiO 2 and diamond like carbon (DLC) substrates. Plasmon dispersion graphene on diamond like carbon (DLC) q W W0 W0 28nm dead layer asymmetric lineshape Plasmon dispersion graphene on SiO2 sp1 806cm1 sp 2 1168cm1 op 1598cm1 Plasmon damping G 1 G01 a Gpl1 ph W Plasmon damping Comparison between graphene on SiO 2 and graphene on DLC Doping dependence Conclusions. Open questions Plasmon dispersion can be accurately measured in nanoribbons. Plasmon linewidth can be explained by simple mechanisms The main decay channel at high frequencies is decay into optical phonons and electron-hole pairs The role of other decay channels is in reasonable agreement with simple estimates Coulomb blockade, interplay between plasmons and dc transport