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On-Chip Andreev Devices: Hard Superconducting Gap and Quantum Transport in Ballistic Nb-In 0.75 Ga 0.25 As-Quantum-Well-Nb Josephson Junctions

Delfanazari, K; Puddy, RK; Ma, P; Yi, T; Cao, M; Gul, Y; Farrer, I; ... Smith, CG; + view all (2017) On-Chip Andreev Devices: Hard Superconducting Gap and Quantum Transport in Ballistic Nb-In 0.75 Ga 0.25 As-Quantum-Well-Nb Josephson Junctions. Advanced Materials , 29 (37) , Article 1701836. 10.1002/adma.201701836. Green open access

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Abstract

A superconducting hard gap in hybrid superconductor–semiconductor devices has been found to be necessary to access topological superconductivity that hosts Majorana modes (non-Abelian excitation). This requires the formation of homogeneous and barrier-free interfaces between the superconductor and semiconductor. Here, a new platform is reported for topological superconductivity based on hybrid Nb–In0.75Ga0.25As-quantum-well–Nb that results in hard superconducting gap detection in symmetric, planar, and ballistic Josephson junctions. It is shown that with careful etching, sputtered Nb films can make high-quality and transparent contacts to the In0.75Ga0.25As quantum well, and the differential resistance and critical current measurements of these devices are discussed as a function of temperature and magnetic field. It is demonstrated that proximity-induced superconductivity in the In0.75Ga0.25As-quantum-well 2D electron gas results in the detection of a hard gap in four out of seven junctions on a chip with critical current values of up to 0.2 µA and transmission probabilities of >0.96. The results, together with the large g-factor and Rashba spin–orbit coupling in In0.75Ga0.25As quantum wells, which indeed can be tuned by the indium composition, suggest that the Nb–In0.75Ga0.25As–Nb system can be an excellent candidate to achieve topological phase and to realize hybrid topological superconducting devices.

Type: Article
Title: On-Chip Andreev Devices: Hard Superconducting Gap and Quantum Transport in Ballistic Nb-In 0.75 Ga 0.25 As-Quantum-Well-Nb Josephson Junctions
Open access status: An open access version is available from UCL Discovery
DOI: 10.1002/adma.201701836
Publisher version: http://dx.doi.org/10.1002/adma.201701836
Language: English
Additional information: Copyright © 2017 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA Weinheim. This is an open access article under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits use, distribution and reproduction in any medium, provided the original work is properly cited. The copyright line for this article was changed on 15 Aug 2017 after original online publication.
Keywords: hybrid superconductor–semiconductor junctions; Josephson junctions; quantum computing; topological superconductivity
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology
URI: http://discovery.ucl.ac.uk/id/eprint/10038959
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