Ballistic Majorana nanowire devices

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Abstract

Majorana modes are zero-energy excitations of a topological superconductor that exhibit non-Abelian statistics1,2,3. Following proposals for their detection in a semiconductor nanowire coupled to an s-wave superconductor4,5, several tunnelling experiments reported characteristic Majorana signatures6,7,8,9,10,11. Reducing disorder has been a prime challenge for these experiments because disorder can mimic the zero-energy signatures of Majoranas12,13,14,15,16, and renders the topological properties inaccessible17,18,19,20. Here, we show characteristic Majorana signatures in InSb nanowire devices exhibiting clear ballistic transport properties. Application of a magnetic field and spatial control of carrier density using local gates generates a zero bias peak that is rigid over a large region in the parameter space of chemical potential, Zeeman energy and tunnel barrier potential. The reduction of disorder allows us to resolve separate regions in the parameter space with and without a zero bias peak, indicating topologically distinct phases. These observations are consistent with the Majorana theory in a ballistic system21, and exclude the known alternative explanations that invoke disorder12,13,14,15,16 or a nonuniform chemical potential22,23.

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Fig. 1: Hybrid device and ballistic transport properties.
Fig. 2: Zero bias peak and its dependence on magnetic field and local gate voltages.
Fig. 3: Dependence of zero bias peak on magnetic field orientation.
Fig. 4: Zero bias peak and phase diagram.

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Acknowledgements

We thank A. R. Akhmerov, O. W. B. Benningshof, M. C. Cassidy, S. Goswami, J. Kammhuber, V. Mourik, M. Quintero-Pérez, J. Shen, M. Wimmer, D. J. van Woerkom and K. Zuo for discussions and assistance. This work has been supported by the Netherlands Organisation for Scientific Research (NWO), European Research Council (ERC) and Microsoft Corporation Station Q.

Author information

Ö.G., H.Z. and J.D.S.B fabricated the devices, performed the measurements, and analysed the data. M.W.A.d.M. contributed to the device fabrication. D.C., S.P. and E.P.A.M.B. grew the InSb nanowires. A.G. contributed to the experiments. K.W. and T.T. synthesized the hBN crystals. L.P.K. supervised the project. Ö.G., H.Z. and J.D.S.B. co-wrote the paper. All authors commented on the manuscript.

Correspondence to Önder Gül or Hao Zhang or Leo P. Kouwenhoven.

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Gül, Ö., Zhang, H., Bommer, J.D.S. et al. Ballistic Majorana nanowire devices. Nature Nanotech 13, 192–197 (2018) doi:10.1038/s41565-017-0032-8

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