Dielectric screening and plasmon resonances in bilayer graphene

Abstract

The plasmon structure of intrinsic and extrinsic bilayer graphene is investigated in the framework of ab initio time-dependent density-functional theory (TDDFT) at the level of the random-phase approximation (RPA). A two-step scheme is adopted, where the electronic ground state of a periodically repeated slab of bilayer graphene is first determined with full inclusion of the anisotropic band structure and the interlayer interaction; a Dyson-like equation is then solved self-consistently in order to calculate the so-called density-response function of the many-electron system. A two-dimensional correction is subsequently applied in order to eliminate the artificial interaction between the replicas. The energy range below ∼30 eV is explored, focusing on the spectrum of single-particle excitations and plasmon resonances induced by external electrons or photons. The high-energy loss features of the π and σ + π plasmons, particularly their anisotropic dispersions, are predicted and discussed in relation with previous calculations and experiments performed on monolayer and bilayer graphene. At the low-energy end, the energy-loss function is found to be (i) very sensitive to the injected charge carrier density in doped bilayer graphene and (ii) highly anisotropic. Furthermore, various plasmon modes are predicted to exist and are analyzed with reference to the design of novel nanodevices.

Plasmon Modes of Graphene Nanoribbons with Periodic Planar Arrangements

“…The v GG terms have been proved to efficiently cut off the spurious interaction between replicas of planar graphenebased systems [18,[45][46][47]. Finally, the EL spectra were computed by…”

“…Some recent calculations have reported the existence of two extrinsic plasmons in MG and bilayer graphene (BLG) [17][18][19][20]. In particular, the plasmon coupling in BLG [20] shares some common features with 5AGNR at similar doping conditions; i.e., one of the two modes disperses like q 1/2 and the other is quasivertical.…”

“…A serious drawback stems from the long-range character of the Coulomb potential, which allows nonnegligible interactions between repeated planar arrays even at large distances. To cut off this unwanted phenomenon, we replace v 0 GG by the truncated Fourier integral [18,19,[45][46][47] …”

“…Plasmon-related technologies are expected to receive a burst from nanocarbon architectures [1][2][3][4][5][6][7][8][9][10], due to one of the fascinating features of monolayer graphene (MG) [11], i.e., its extrinsic plasmon modes at terahertz (THz) frequencies [12][13][14][15][16][17][18][19][20]. These show much stronger confinement, larger tunability and lower losses [21] compared to conventional plasmonic materials, such as silver or gold.…”

“…Plasmons are quantized oscillations of the valence electron density in metals, metal-dielectric interfaces and nanostructures, being usually excited by light or electronbeam radiation. Plasmon-related technologies are expected to receive a burst from nanocarbon architectures [1-10], due to one of the fascinating features of monolayer graphene (MG) [11], i.e., its extrinsic plasmon modes at terahertz (THz) frequencies [12][13][14][15][16][17][18][19][20]. These show much stronger confinement, larger tunability and lower losses [21] compared to conventional plasmonic materials, such as silver or gold.…”