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Hard gap in epitaxial semiconductor–superconductor nanowires

Abstract

Many present and future applications of superconductivity would benefit from electrostatic control of carrier density and tunnelling rates, the hallmark of semiconductor devices. One particularly exciting application is the realization of topological superconductivity1 as a basis for quantum information processing2,3. Proposals in this direction based on the proximity effect in semiconductor nanowires are appealing because the key ingredients are currently in hand4,5. However, previous instances of proximitized semiconductors show significant tunnelling conductance below the superconducting gap, suggesting a continuum of subgap states—a situation that nullifies topological protection6,7. Here, we report a hard superconducting gap induced by the proximity effect in a semiconductor, using epitaxial InAs–Al semiconductor–superconductor nanowires. The hard gap, together with favourable material properties and gate-tunability, makes this new hybrid system attractive for a number of applications, as well as fundamental studies of mesoscopic superconductivity.

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Figure 1: Epitaxial full-shell device and hard induced gap.
Figure 2: Gate dependence of conductance of full-shell device.
Figure 3: Comparing quantum point contact and quantum dot devices.
Figure 4: Magnetic field and temperature dependence of induced gaps.
Figure 5: Epitaxial half-shell device and gate-tunability of InAs core.

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Acknowledgements

The authors thank E. Johnson for assistance with electron microscopy and K. Flensberg for discussions. This research was supported by Microsoft Project Q, the Danish National Research Foundation, the Carlsberg Foundation, the Villum Foundation, the Lundbeck Foundation and the European Commission.

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Contributions

P.K., T.S.J. and J.N. developed the nanowire materials. W.C. and S.A. fabricated the devices and carried out the measurements with input from F.K., T.S.J. and C.M. All authors contributed to analysing and interpreting the data and to writing the manuscript.

Corresponding author

Correspondence to C. M. Marcus.

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The authors declare no competing financial interests.

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Chang, W., Albrecht, S., Jespersen, T. et al. Hard gap in epitaxial semiconductor–superconductor nanowires. Nature Nanotech 10, 232–236 (2015). https://doi.org/10.1038/nnano.2014.306

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