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Edge-mode superconductivity in a two-dimensional topological insulator

Abstract

Topological superconductivity is an exotic state of matter that supports Majorana zero-modes, which have been predicted to occur in the surface states of three-dimensional systems, in the edge states of two-dimensional systems, and in one-dimensional wires1,2. Localized Majorana zero-modes obey non-Abelian exchange statistics, making them interesting building blocks for topological quantum computing3,4. Here, we report superconductivity induced in the edge modes of semiconducting InAs/GaSb quantum wells, a two-dimensional topological insulator5,6,7,8,9,10. Using superconducting quantum interference we demonstrate gate-tuning between edge-dominated and bulk-dominated regimes of superconducting transport. The edge-dominated regime arises only under conditions of high-bulk resistivity, which we associate with the two-dimensional topological phase. These experiments establish InAs/GaSb as a promising platform for the confinement of Majoranas into localized states, enabling future investigations of non-Abelian statistics.

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Figure 1: Band structure and SQI patterns.
Figure 2: Device layout and normal state transport.
Figure 3: Josephson effect in device A (cooldown 2).
Figure 4: SQI patterns and corresponding current density profiles for device A (cooldown 1).
Figure 5: 2Φ0-periodic quantum interference pattern.

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Acknowledgements

The authors thank A. Akhmerov, D. Pikulin, M. Wimmer, T. Hyart, B. Baxevanis, C. Beenakker and A. Geresdi for valuable discussions and comments and K. Zuo for assistance with the dilution refrigerator. This work has been supported by funding from the Netherlands Foundation for Fundamental Research on Matter (FOM) and Microsoft Corporation Station Q. V.S.P. acknowledges funding from the Netherlands Organisation for Scientific Research (NWO) through a VENI grant. C.C. and W.W. acknowledge funding by the Swiss National Science Foundation (SNF).

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V.S.P., A.J.A.B. and F.Q. fabricated the devices and performed the measurements. C.C. and W.W. provided the InAs/GaSb heterostructures. V.S.P., A.J.A.B., F.Q., M.C.C. and L.P.K. contributed to the experiments and all authors discussed the results and edited the manuscript.

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Correspondence to Leo P. Kouwenhoven.

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The authors declare no competing financial interests.

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Pribiag, V., Beukman, A., Qu, F. et al. Edge-mode superconductivity in a two-dimensional topological insulator. Nature Nanotech 10, 593–597 (2015). https://doi.org/10.1038/nnano.2015.86

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