Graphene's πα
Plate 058 Physics Poster
Plate 58 speaks for itself: “2.3% dark.”
The Physics
Electrons in graphene behave like massless Dirac particles with a linear dispersion. As a result a single atomic layer absorbs a fraction πα of visible light, set only by the fine-structure constant.
E = ± ħ v_F |k|
- E: electron energy, J
- ħ: reduced Planck constant, J s
- v_F: Fermi velocity ≈ 10⁶ m s⁻¹
- k: wavevector from the Dirac point, m⁻¹
- α: fine-structure constant, dimensionless
One layer absorbs πα ≈ 2.29%. It depends only on α.
Sources
- R. R. Nair et al., Science 320, 1308 (2008).
On the poster
Plate 058, “Graphene's πα”: the pixel-art plate with its slogan “2.3% dark.”, the key equation and the facts panel shown above. Pixelated Physics. Physics. Personified.
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