Zero-bias peaks and splitting in an Al–InAs nanowire topological superconductor as a signature of Majorana fermions

Abstract

Majorana fermions are the only fermionic particles that are expected to be their own antiparticles. Although elementary particles of the Majorana type have not been identified yet, quasi-particles with Majorana-like properties, born from interacting electrons in the solid, have been predicted to exist. Here, we present thorough experimental studies, backed by numerical simulations, of a system composed of an aluminium superconductor in proximity to an indium arsenide nanowire, with the latter possessing strong spin–orbit coupling and Zeeman splitting. An induced one-dimensional topological superconductor, supporting Majorana fermions at both ends, is expected to form. We concentrate on the characteristics of a distinct zero-bias conductance peak and its splitting in energy—both appearing only with a small magnetic field applied along the wire. The zero-bias conductance peak was found to be robustly tied to the Fermi energy over a wide range of system parameters. Although not providing definite proof of a Majorana state, the presented data and the simulations support its existence.

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Figure 1: Energy dispersion of InAs nanowire excitations (Bogoliubov–de Gennes spectrum), in proximity to an Al superconductor.
Figure 2: A suspended Al–InAs nanowire on gold pedestals above p-type silicon.
Figure 3: Evolution of the ZBP with chemical potential and magnetic field, for the VRG range 1.17–1.24 V at VGG = −18.3 V for a type II device (D4).
Figure 4: Low-bias conductance as a function of applied magnetic field parallel to the wire axis (type II device, D4).
Figure 5: Low-bias conductance as a function of applied magnetic field parallel to the wire axis (type II device, D4), at a higher chemical potential.
Figure 6: Temperature and magnetic field orientation dependence of the ZBP of device D3 at B = 70 mT.

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Acknowledgements

We thank A. Haim, A. Stern, F. von Oppen and G. Refael for useful discussions. We are grateful to R. Popovitz-Biro and D. Mahalu for their professional contribution and to A. Kretinin for laying the groundwork for nanowire device physics, and S. Ilani and A. Joshua for enabling us to perform the tilted field measurement. M.H. acknowledges the partial support of the Israeli Science Foundation (ISF), the Minerva foundation, the US-Israel Bi-National Science Foundation (BSF) and the European Research Council under the European Community’s Seventh Framework Program (FP7/2007-2013)/ERC Grant agreement # 227716. Y.O. acknowledges the partial support of the DFG, Minerva and that of the BSF. H.S. acknowledges the partial support of the ISF and the Israeli Ministry of Science and Technology (IMOST).

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A.D. and Y.R. contributed to sample design, device fabrication, set-up, data acquisition, analysis and writing of the paper. M.H. contributed to design, data interpretation and writing of the paper. Y.M. contributed to theory, simulations and writing of the paper. Y.O. contributed to theory, simulations, experimental insight and writing of the paper. H.S contributed to the Au-assisted vapour-liquid–solid molecular beam epitaxy growth and structural study of InAs nanowires, discussions and editing of the manuscript.

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Correspondence to Moty Heiblum.

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Das, A., Ronen, Y., Most, Y. et al. Zero-bias peaks and splitting in an Al–InAs nanowire topological superconductor as a signature of Majorana fermions. Nature Phys 8, 887–895 (2012). https://doi.org/10.1038/nphys2479

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