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Normal, superconducting and topological regimes of hybrid double quantum dots

Nature Nanotechnology volume 12, pages 212–217 (2017)Cite this article

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Abstract

Epitaxial semiconductor–superconductor hybrid materials are an excellent basis for studying mesoscopic and topological superconductivity, as the semiconductor inherits a hard superconducting gap while retaining tunable carrier density1. Here, we investigate double-quantum-dot structures made from InAs nanowires with a patterned epitaxial Al two-facet shell2 that proximitizes two gate-defined segments along the nanowire. We follow the evolution of mesoscopic superconductivity and charging energy in this system as a function of magnetic field and voltage-tuned barriers. Interdot coupling is varied from strong to weak using side gates, and the ground state is varied between normal, superconducting and topological regimes by applying a magnetic field. We identify the topological transition by tracking the spacing between successive co-tunnelling peaks as a function of axial magnetic field3 and show that the individual dots host weakly hybridized Majorana modes.

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Figure 1: Double quantum dot with controllable coupling and superconductivity.
Figure 2: Tuning interdot coupling.
Figure 3: Addition energy as a function of interdot coupling.
Figure 4: Signatures of Majorana modes via even–odd peak spacing along co-tunnelling lines.

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Acknowledgements

The authors acknowledge support from the Danish National Research Foundation and Microsoft Research. C.M.M. acknowledges support from the Villum Foundation.

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Authors and Affiliations

  1. Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark

    D. Sherman, J. S. Yodh, S. M. Albrecht, J. Nygård, P. Krogstrup & C. M. Marcus

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  1. D. Sherman
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  2. J. S. Yodh
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  3. S. M. Albrecht
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Contributions

P.K. and J.N. developed the nanowire materials. D.S. fabricated the devices. D.S., J.S.Y. and S.M.A. carried out the measurements with input from C.M.M. D.S. analysed the data. D.S., J.S.Y. and C.M.M. wrote the paper. All authors discussed the results and commented on the manuscript.

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Correspondence to C. M. Marcus.

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Sherman, D., Yodh, J., Albrecht, S. et al. Normal, superconducting and topological regimes of hybrid double quantum dots. Nature Nanotech 12, 212–217 (2017). https://doi.org/10.1038/nnano.2016.227

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