Abstract
The long-sought yet elusive Majorana fermion1 is predicted to arise from a combination of a superconductor and a topological insulator2,3,4. An essential step in the hunt for this emergent particle is the unequivocal observation of supercurrent in a topological phase. Here, direct evidence for Josephson supercurrents in superconductor (Nb)–topological insulator (Bi2Te3)–superconductor electron-beam fabricated junctions is provided by the observation of clear Shapiro steps under microwave irradiation, and a Fraunhofer-type dependence of the critical current on magnetic field. Shubnikov–de Haas oscillations in magnetic fields up to 30 T reveal a topologically non-trivial two-dimensional surface state. This surface state is attributed to mediate the ballistic Josephson current despite the fact that the normal state transport is dominated by diffusive bulk conductivity. The lateral Nb–Bi2Te3–Nb junctions hence provide prospects for the realization of devices supporting Majorana fermions5.
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Change history
01 March 2012
In the version of this Letter originally published online, the name of the eighth author was represented incorrectly; it should have read W. G. van der Wiel. This error has been corrected in all versions of the Letter.
20 December 2012
In the version of this Letter originally published, in Fig. 2b, the label on the y axis should have been 'mΩ'. On page 1, the section beginning "Now the existence of the topological surface states..." in the second paragraph has been rephrased. These errors have been corrected in the HTML and PDF versions.
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Acknowledgements
We acknowledge useful discussions with C. W. J. Beenakker, B. C. Kaas, M. Fuhrer, C. G. Molenaar, L. Molenkamp, N. Nagaosa, Y. V. Nazarov and Y. Tanaka. This work is supported by the Netherlands Organization for Scientific Research (NWO) through VIDI and VICI grants, by the Dutch Foundation for Fundamental Research on Matter, and by the Australian Research Council through a Discovery project.
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M.V. designed, fabricated and measured the devices. M.S. and M.H. contributed to the fabrication. X.L.W. supplied the crystals. V.K.G. and T.G. contributed to the measurements. M.V., U.Z., W.G.v.d.W., A.A.G., H.H. and A.B. analysed the data and wrote the manuscript.
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Veldhorst, M., Snelder, M., Hoek, M. et al. Josephson supercurrent through a topological insulator surface state. Nature Mater 11, 417–421 (2012). https://doi.org/10.1038/nmat3255
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DOI: https://doi.org/10.1038/nmat3255
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