Reexamination of the effective fine structure constant of graphene as measured in graphite

Yu Gan, Gilberto A. De La Peña, Anshul Kogar, Bruno Uchoa, Diego Casa, Thomas Gog, Eduardo Fradkin, Peter Abbamonte

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We present a refined and improved study of the influence of screening on the effective fine structure constant of graphene, α∗, as measured in graphite using inelastic x-ray scattering. This followup to our previous study [J. P. Reed, Science 330, 805 (2010)SCIEAS0036-807510.1126/science.1190920] was carried out with two times better energy resolution, five times better momentum resolution, and an improved experimental setup with lower background. We compare our results to random-phase approximation (RPA) calculations and evaluate the relative importance of interlayer hopping, excitonic corrections, and screening from high energy excitations involving the σ bands. We find that the static, limiting value of α∗ falls in the range 0.25-0.35, which is higher than our previous result of 0.14, but still below the value expected from RPA. We show the reduced value is not a consequence of interlayer hopping effects, which were ignored in our previous analysis, but of a combination of excitonic effects in the π→π∗ particle-hole continuum, and background screening from the σ-bonded electrons. We find that σ-band screening is extremely strong at distances of less than a few nanometers, and should be highly effective at screening out short-distance, Hubbard-like interactions in graphene as well as other carbon allotropes.

Original languageEnglish (US)
Article number195150
JournalPhysical Review B
Issue number19
StatePublished - May 24 2016

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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