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arXiv · 0810.1269

Measurement of the Optical Conductivity of Graphene

Kin Fai Mak·Matthew Y. Sfeir·Yang Wu·Chun Hung Lui·James A. Misewich·Tony F. Heinz
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Abstract

Optical reflectivity and transmission measurements over photon energies between 0.2 and 1.2 eV were performed on single-crystal graphene samples on a transparent SiO2 substrate. For photon energies above 0.5 eV, graphene yielded a spectrally flat optical absorbance of (2.3 +/- 0.2)%. This result is in agreement with a constant absorbance of pi*alpha, or a sheet conductivity of pi*e^2/2h, predicted within a model of non-interacting massless Dirac Fermions. This simple result breaks down at lower photon energies, where both spectral and sample-to-sample variations were observed. This "non-universal" behavior is explained by including the effects of doping and finite temperature, as well as contributions from intraband transitions.

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Kin Fai Mak, Matthew Y. Sfeir, Yang Wu, Chun Hung Lui, James A. Misewich, Tony F. Heinz. 2009-08-03. Measurement of the Optical Conductivity of Graphene. https://doi.org/10.1103/physrevlett.101.196405

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