title: Electronic excitations in graphene in the 1-50 eV range: the π and π + σ peaks are not plasmons.
abstract: The field of plasmonics relies on light coupling strongly to plasmons as collective excitations. The energy loss function of graphene is dominated by two peaks at ∼5 and ∼15 eV, known as π and π + σ plasmons, respectively. We use electron energy-loss spectroscopy in an aberration-corrected scanning transmission electron microscope and density functional theory to show that between 1 to 50 eV, these prominent π and π + σ peaks are not plasmons, but single-particle interband excitations.
authors.affiliation: SUNY College of Nanoscale Science and Engineering , 257 Fuller Road, Albany, New York 12203, United States.
authors.forename: Florence J
authors.initials: FJ
authors.lastname: Nelson
authors.forename: Juan-Carlos
authors.initials: JC
authors.lastname: Idrobo
authors.forename: John D
authors.initials: JD
authors.lastname: Fite
authors.forename: Zoran L
authors.initials: ZL
authors.lastname: Mišković
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Pennycook
authors.forename: Sokrates T
authors.initials: ST
authors.lastname: Pantelides
authors.forename: Ji Ung
authors.initials: JU
authors.lastname: Lee
authors.forename: Alain C
authors.initials: AC
authors.lastname: Diebold