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Gigahertz quantized charge pumping in graphene quantum dots

Nature Nanotechnology volume 8, pages 417–420 (2013)Cite this article

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Abstract

Single-electron pumps are set to revolutionize electrical metrology by enabling the ampere to be redefined in terms of the elementary charge of an electron1. Pumps based on lithographically fixed tunnel barriers in mesoscopic metallic systems2 and normal/superconducting hybrid turnstiles3 can reach very small error rates, but only at megahertz pumping speeds that correspond to small currents of the order of picoamperes. Tunable barrier pumps in semiconductor structures are operated at gigahertz frequencies1,4, but the theoretical treatment of the error rate is more complex and only approximate predictions are available5. Here, we present a monolithic, fixed-barrier single-electron pump made entirely from graphene that performs at frequencies up to several gigahertz. Combined with the record-high accuracy of the quantum Hall effect6 and proximity-induced Josephson junctions7, quantized-current generation brings an all-graphene closure of the quantum metrological triangle within reach8,9. Envisaged applications for graphene charge pumps outside quantum metrology include single-photon generation via electron–hole recombination in electrostatically doped bilayer graphene reservoirs10, single Dirac fermion emission in relativistic electron quantum optics11 and read-out of spin-based graphene qubits in quantum information processing12.

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Figure 1: Pumping mechanism in a graphene double quantum dot.
Figure 2: Gigahertz quantized charge pumping (T = 300 mK).
Figure 3: Frequency dependence of the pumped current (T = 300 mK).
Figure 4: Quantization accuracy at low frequency (T = 1.2 K).

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Acknowledgements

This work was supported financially by the European Graphene-based Nanoelectronic Devices project (ICT/FET, Contract No. 215752), an Engineering and Physical Sciences Research Council/National Physical Laboratory (NPL) Joint Postdoctoral Partnership and the NPL Strategic Research Programme.

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Authors and Affiliations

  1. National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK

    M. R. Connolly, S. P. Giblin, M. Kataoka, J. D. Fletcher & T. J. B. M. Janssen

  2. Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK

    M. R. Connolly, K. L. Chiu, C. Chua, J. P. Griffiths, G. A. C. Jones & C. G. Smith

  3. Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK

    V. I. Fal'ko

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  1. M. R. Connolly
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Contributions

M.R.C. conceived the study jointly with T.J.B.M.J. and C.G.S., designed the devices with K.L.C., implemented the experiment with S.P.G., M.K. and J.D.F., and wrote the manuscript with contributions from S.P.G., T.J.B.M.J. and V.I.F. C.C. developed the device simulations with contributions from M.R.C. K.L.C. fabricated the devices with contributions from M.R.C., J.P.G. and G.A.C.J.

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Correspondence to M. R. Connolly.

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The authors declare no competing financial interests.

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Connolly, M., Chiu, K., Giblin, S. et al. Gigahertz quantized charge pumping in graphene quantum dots. Nature Nanotech 8, 417–420 (2013). https://doi.org/10.1038/nnano.2013.73

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