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Inducing superconducting correlation in quantum Hall edge states

Nature Physics volume 13, pages 693–698 (2017)Cite this article

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Abstract

The quantum Hall (QH) effect supports a set of chiral edge states at the boundary of a two-dimensional system. A superconductor (SC) contacting these states can provide correlations of the quasiparticles in the dissipationless edge states. Here we fabricated highly transparent and nanometre-scale SC junctions to graphene. We demonstrate that the QH edge states can couple via superconducting correlations through the SC electrode narrower than the superconducting coherence length. We observe that the chemical potential of the edge state exhibits a sign reversal across the SC electrode. This provides direct evidence of conversion of the incoming electron to the outgoing hole along the chiral edge state, termed crossed Andreev conversion (CAC). We show that CAC can successfully describe the temperature, bias and SC electrode width dependences. This hybrid SC/QH system could provide a novel route to create isolated non-Abelian anyonic zero modes, in resonance with the chiral edge states.

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Figure 1: Magnetic field dependence of Andreev reflection.
Figure 2: Temperature dependence of quantum Hall edge chemical potentials at B = 8 T.
Figure 3: Bias dependence of the negative response at B = 8 T and ν = 2.
Figure 4: Exponential width dependence on negative response at B = 8 T and ν = 2.

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Acknowledgements

We thank S.-C. Zhang, B. Halperin and J. Alicea for fruitful discussions. The major experimental work, including sample preparation and measurement, is supported by DOE (DE-SC0012260). The Harvard collaboration was supported by the Science and Technology Center for Integrated Quantum Materials, NSF Grant No. DMR-1231319. G.-H.L. acknowledges support from the Nano Material Technology Development Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2012M3A7B4049966). P.K. acknowledges partial support from the Gordon and Betty Moore Foundation’s EPiQS Initiative through Grant GBMF4543 and ARO (W911NF-14-1-0638). K.-F.H. is supported by NSF (EFRI 2-DARE 1542807). A.Y. acknowledges support from the US DOE Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under award de-sc0001819. D.S.W. acknowledges the support from the National Science Foundation Graduate Research Fellowship under Grant No. DGE1144152. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan and JSPS KAKENHI Grant Numbers JP26248061, JP15K21722 and JP25106006. A portion of this work was performed at the Center for Nanoscale Systems at Harvard, supported in part by an NSF NNIN award ECS-00335765.

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  1. Sean Hart

    Present address: Present address: Department of Physics, Stanford University, Stanford, California 94305, USA.,

Authors and Affiliations

  1. Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA

    Gil-Ho Lee, Ko-Fan Huang, Di S. Wei, Sean Hart, Amir Yacoby & Philip Kim

  2. Department of Electrical Engineering, M.I.T., Cambridge, Massachusetts 02138, USA

    Dmitri K. Efetov

  3. ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain

    Dmitri K. Efetov

  4. National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan

    Takashi Taniguchi & Kenji Watanabe

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Contributions

G.-H.L. and P.K. conceived the idea and designed the project. P.K. supervised the project. G.-H.L., K.-F.H. and S.H. fabricated the devices. T.T. and K.W. provided single crystals of hBN. G.-H.L. and D.S.W. performed the measurements. G.-H.L. and P.K. analysed the data and wrote the manuscript. G.-H.L., K.-F.H., D.K.E., D.S.W., S.H., A.Y. and P.K. contributed to the discussion.

Corresponding author

Correspondence to Philip Kim.

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The authors declare no competing financial interests.

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Lee, GH., Huang, KF., Efetov, D. et al. Inducing superconducting correlation in quantum Hall edge states. Nature Phys 13, 693–698 (2017). https://doi.org/10.1038/nphys4084

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