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Dirac charge dynamics in graphene by infrared spectroscopy

Nature Physics volume 4, pages 532–535 (2008)Cite this article

Abstract

A remarkable manifestation of the quantum character of electrons in matter is offered by graphene, a single atomic layer of graphite. Unlike conventional solids where electrons are described with the Schrödinger equation, electronic excitations in graphene are governed by the Dirac hamiltonian1. Some of the intriguing electronic properties of graphene, such as massless Dirac quasiparticles with linear energy–momentum dispersion, have been confirmed by recent observations2,3,4,5. Here, we report an infrared spectromicroscopy study of charge dynamics in graphene integrated in gated devices. Our measurements verify the expected characteristics of graphene and, owing to the previously unattainable accuracy of infrared experiments, also uncover significant departures of the quasiparticle dynamics from predictions made for Dirac fermions in idealized, free-standing graphene. Several observations reported here indicate the relevance of many-body interactions to the electromagnetic response of graphene.

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Figure 1: The reflectance R(ω) and transmission T(ω) of a graphene device under applied gate voltages.
Figure 2: The optical conductivity of graphene at different voltages.
Figure 3: The Fermi energy EF and the ratio of EF to the Fermi wave vector EF/ℏkF.

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Acknowledgements

Work at UCSD is supported by the DOE (No. DE-FG02-00ER45799). Research at Columbia University is supported by the DOE (No. DE-AIO2-04ER46133 and No. DE-FG02-05ER46215), NSF (No. DMR-03-52738 and No. CHE-0117752), NYSTAR and the Keck Foundation. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract No. DE-AC02-05CH11231.

Author information

Authors and Affiliations

  1. Department of Physics, University of California, San Diego, La Jolla, California 92093, USA

    Z. Q. Li & D. N. Basov

  2. Department of Physics, Columbia University, New York 10027, USA

    E. A. Henriksen, Z. Jiang, P. Kim & H. L. Stormer

  3. National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA

    Z. Jiang

  4. Advanced Light Source Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

    Z. Hao & M. C. Martin

  5. Department of Applied Physics and Applied Mathematics, Columbia University, New York 10027, USA

    H. L. Stormer

  6. Bell Labs, Alcatel-Lucent, Murray Hill, New Jersey 07974, USA

    H. L. Stormer

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  1. Z. Q. Li
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  2. E. A. Henriksen
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  3. Z. Jiang
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  4. Z. Hao
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  5. M. C. Martin
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  7. H. L. Stormer
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  8. D. N. Basov
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Correspondence to Z. Q. Li.

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Li, Z., Henriksen, E., Jiang, Z. et al. Dirac charge dynamics in graphene by infrared spectroscopy. Nature Phys 4, 532–535 (2008). https://doi.org/10.1038/nphys989

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