Physics – Condensed Matter – Strongly Correlated Electrons
Scientific paper
2010-11-06
Science, 330, p. 805 (2010)
Physics
Condensed Matter
Strongly Correlated Electrons
28 pages, 10 figures, 2 animations
Scientific paper
Electrons in graphene behave like Dirac fermions, permitting phenomena from high energy physics to be studied in a solid state setting. A key question is whether or not these Fermions are critically influenced by Coulomb correlations. We performed inelastic x-ray scattering experiments on crystals of graphite, and applied reconstruction algorithms to image the dynamical screening of charge in a freestanding, graphene sheet. We found that the polarizability of the Dirac fermions is amplified by excitonic effects, improving screening of interactions between quasiparticles. The strength of interactions is characterized by a scale-dependent, effective fine structure constant, \alpha *(k,\omega), whose value approaches \alpha * ~ 1/7 at low energy and large distances. This value is substantially smaller than the nominal \alpha = 2.2, suggesting that, on the whole, graphene is more weakly interacting than previously believed.
Abbamonte Peter
Casa Diego
Fradkin Eduardo
Gan Yu
Joe Young Il
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