Figure 1From: Collective excitations on a surface of topological insulatorPlasmon dispersions. Plasmon dispersions Ω q at different values of rs. Continuums of intraband (ω <vFq) and interband (ω > 2μ - vFq) single-particle excitations are shaded; pF = μ/vF is the Fermi momentum, μ is the chemical potential.Back to article page