Plasmon dispersion in semimetallic armchair graphene nanoribbons

Abstract

The dispersion relations for plasmons in intrinsic and extrinsic semimetallic armchair graphene nanoribbons (acGNR) are calculated in the random phase approximation using the orthogonal pz-orbital tight binding method. Our model predicts new plasmons for acGNR of odd atomic widths N = 5, 11, 17, . . . Our model further predicts plasmons in acGNR of even atomic width N = 2, 8, 14, . . . related to those found using a Dirac continuum model, but with different quantitative dispersion characteristics. We find that the dispersion of all plasmons in semimetallic acGNR depends strongly on the localization of the pz electronic wavefunctions. We also find that overlap integrals for acGNR behave in a more complex way than predicted by the Dirac continuum model, suggesting that these plasmons will experience a small damping for all q = 0. Plasmons in extrinsic semimetallic acGNR with the chemical potential in the lowest (highest) conduction (valence) band are found to have dispersion characteristics nearly identical to their intrinsic counterparts, with negligible differencs in dispersion arising from the slight differences in overlap integrals for the interband and intraband transitions.

Plasmon Modes of Graphene Nanoribbons with Periodic Planar Arrangements

“…S7(a), where a comparison of the intraband plasmon dispersion of 5AGNR is attempted with the calculations of Ref. [33]. The latter were based on a tight-binding (TB) gapless two-band model at the absolute zero.…”

“…[31], and appears at the same scale as the low-q dispersions of Ref. [33], computed from the TB approximation where 5AGNR is virtually gapless [ Fig. S7(a) in [34]].…”

“…On the theoretical side, density functional and tight-binding (TB) approaches have explored the electronic structure of zigzag and armchair GNRs, with particular attention to the band-gap values of the intrinsic systems, being a major control factor of their plasmonic properties [26][27][28][29][30]. Far fewer studies have been focused on plasmon resonances in GNRs using either a semiclassical electromagnetic picture [31] or a TB scheme [5,32,33], and specializing to THz frequencies. A comprehensive characterization of the dielectric properties of such systems is, however, lacking.…”

A Primer on Surface Plasmon-Polaritons in Graphene

“…This important ambipolar doping effect has opened the tantalizing prospect of real time control of SPPs by using a gate. In addition, the transfer of graphene films to a range of substrates is routine nowadays and has inspired the design of graphene-based structures with unique plasmonic signatures, such as quantum dots (or anti-dots) 39,40,41,42,43 and nanoribbons 44,45,46,47,48 . In this respect, the question of whether the classical description of SPs still holds for finite-size systems, such as quantum dots, is particularly relevant 43 .…”

Third-Order Optical Response of Metallic Armchair Graphene Nanoribbons to an Elliptically-Polarized Terahertz Excitation Field

“…Due to the the geometry and boundary conditions [22][23][24], these two types of GNRs show distinct electronic characteristics in the low energy regime. The linear and nonlinear response of GNRs due to a linearly-polarized electric field were studied in [25][26][27][28][29][30][31].…”