Measurement of the Optical Conductivity of Graphene

Kin Fai Mak, Matthew Y. Sfeir, Yang Wu, Chun Hung Lui, James A. Misewich, and Tony F. Heinz
Phys. Rev. Lett. 101, 196405 – Published 7 November 2008


Optical reflectivity and transmission measurements over photon energies between 0.2 and 1.2 eV were performed on single-crystal graphene samples on a 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 πα, or a sheet conductivity of πe2/2h, predicted within a model of noninteracting massless Dirac fermions. This simple result breaks down at lower photon energies, where both spectral and sample-to-sample variations were observed. This “nonuniversal” behavior is explained by including the effects of doping and finite temperature, as well as contributions from intraband transitions.

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  • Received 28 June 2008


©2008 American Physical Society

Authors & Affiliations

Kin Fai Mak1, Matthew Y. Sfeir2, Yang Wu1, Chun Hung Lui1, James A. Misewich2, and Tony F. Heinz1,*

  • 1Departments of Physics and Electrical Engineering, Columbia University, 538 West 120th Street, New York, New York 10027, USA
  • 2Brookhaven National Laboratory, Upton, New York 11973, USA

  • *Corresponding author:

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Vol. 101, Iss. 19 — 7 November 2008

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