Drude weight, plasmon dispersion, and ac conductivity in doped graphene sheets

Abstract

We demonstrate that the plasmon frequency and Drude weight of the electron liquid in a doped graphene sheet are strongly renormalized by electron-electron interactions even in the longwavelength limit. This effect is not captured by the Random Phase Approximation (RPA), commonly used to describe electron fluids and is due to coupling between the center of mass motion and the pseudospin degree of freedom of the graphene's massless Dirac fermions. Making use of diagrammatic perturbation theory to first order in the electron-electron interaction, we show that this coupling enhances both the plasmon frequency and the Drude weight relative to the RPA value. We also show that interactions are responsible for a significant enhancement of the optical conductivity at frequencies just above the absorption threshold. Our predictions can be checked by far-infrared spectroscopy or inelastic light scattering.

Robust Phonon-Plasmon Coupling in Quasifreestanding Graphene on Silicon Carbide

“…The resulting charge carrier mobility and effective mass values are compiled in table I together with the other parameters. The effective masses are about one order of magnitude lower than the theoretical calculations in the long wavelength limit by Abedinpour et al [30] suggest. However, compared to optical measurements [31], HREELS measures at a rather large momentum transfer thus suggesting a momentum dispersion of the effective mass.…”

Coulomb drag

“…Theoretically, plasmons were studied in graphene monolayers (at T = 0) in Hwang and Das Sarma (2007) . Renormalization of the plasmon spectrum due to electronelectron interaction was considered in Abedinpour et al (2011). Experimentally, plasmons were observed in graphene on SiO 2 substrate (Fei et al, 2011(Fei et al, , 2012, graphene-insulator stacks (Yan et al, 2012a), and in graphene micro-ribbon arrays (Ju et al, 2011).…”

Plasmonic excitations in Coulomb-coupledN-layer graphene structures

“…The measured frequency and weight enhancement of the in-phase optical plasmon mode follows, respectively, the square-root and the linear dependence on the number of graphene sheets in GMLS, i.e. √ N and N , which differs from the weak inlayer density dependence, n 1/4 and n 1/2 , obtained respectively for the plasmon fre- quency and its weight both in single- [25][26][27][28][29] and doublelayer [39][40][41][42] graphene structures. This effect is strikingly different from that in conventional two-dimensional systems in semiconductors where, if exchange and correlations effects 59 are neglected, the in-phase plasmon mode in a symmetrically balanced double-layer system behaves similarly to that in an individual layer with the doubled density.…”

“…Particularly, electron-phonon interaction phenomena have become a subject of active study in single-layer graphene structures in zero [16][17][18][19] and finite magnetic fields [20][21][22][23] . Substantial efforts have been directed towards the investigation of the linear response of doped graphene 24 and of the charge density excitations [25][26][27][28][29] and of such complex quasiparticles as plasmarons 30,31 and plasmon-phonon complexes 32 . Recently, the experimental realization of graphene double-layer structures coupled only via the Coulomb interaction [33][34][35][36][37][38] has attracted substantial theoretical interest in studying the double-layer plasmon effects [39][40][41][42] and the frictional drag 43 in two spatially separated graphene layers [44][45][46][47][48][49][50][51][52] as powerful tools for probing interaction effects of massless Dirac fermions.…”