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Visualization of charge transport through Landau levels in graphene

Nature Physics volume 6, pages 870–874 (2010)Cite this article

Abstract

Band bending and the associated spatially inhomogeneous population of Landau levels play a central role in the physics of the quantum Hall effect (QHE) by constraining the pathways for charge-carrier transport and scattering1. Recent progress in understanding such effects in low-dimensional carrier gases in conventional semiconductors has been achieved by real-space mapping using local probes2,3. Here, we use spatially resolved photocurrent measurements in the QHE regime to study the correlation between the distribution of Landau levels and the macroscopic transport characteristics in graphene. Spatial maps show that the net photocurrent is determined by hot carriers transported to the periphery of the graphene channel, where QHE edge states provide efficient pathways for their extraction to the contacts. The photocurrent is sensitive to the local filling factor, which allows us to reconstruct the local charge density in the entire conducting channel of a graphene device.

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Figure 1: Photocurrent measurements on graphene devices.
Figure 2: Spatial photocurrent maps for different gate voltages at B=9 T.
Figure 3: VG dependence of photocurrent across the device, and photocurrent-generation mechanism.
Figure 4: Carrier relaxation and photocurrent collection in graphene devices in the QHE regime.

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Acknowledgements

Work carried out under the auspices of the US Department of Energy under contract DE-AC02-98CH1-886. Y.Z. acknowledges financial support from NSF contract DMR-0705131.

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Authors and Affiliations

  1. Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA

    G. Nazin, E. Sutter & P. Sutter

  2. Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA

    Y. Zhang

  3. Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA

    L. Zhang

Authors
  1. G. Nazin
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  2. Y. Zhang
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  3. L. Zhang
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  4. E. Sutter
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  5. P. Sutter
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Contributions

P.S., E.S. and G.N. designed the study; G.N. carried out the experiments and analysed the data; Y.Z. and L.Z. provided samples; G.N., P.S. and E.S. wrote the paper; all authors commented on the manuscript.

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Correspondence to P. Sutter.

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The authors declare no competing financial interests.

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Nazin, G., Zhang, Y., Zhang, L. et al. Visualization of charge transport through Landau levels in graphene. Nature Phys 6, 870–874 (2010). https://doi.org/10.1038/nphys1745

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