Electron polarization function and plasmons in metallic armchair graphene nanoribbonsElectron polarization function and plasmons in metallic armchair graphene nanoribbons
Faculty of Sciences. Physics
Condensed Matter Theory
2015Lancaster, Pa, 2015
Physical review : B : condensed matter and materials physics. - Lancaster, Pa, 1998 - 2015
91(2015):20, 6 p.
University of Antwerp
Plasmon excitations in metallic armchair graphene nanoribbons are investigated using the random phase approximation. An exact analytical expression for the polarization function of Dirac fermions is obtained, valid for arbitrary temperature and doping. We find that at finite temperatures, due to the phase space redistribution among inter-band and intra-band electronic transitions in the conduction and valence bands, the full polarization function becomes independent of temperature and position of the chemical potential. It is shown that for a given width of nanoribbon there exists a single plasmon mode whose energy dispersion is determined by the graphene's fine structure constant. In the case of two Coulomb-coupled nanoribbons, this plasmon splits into in-phase and out-of-phase plasmon modes with splitting energy determined by the inter-ribbon spacing.