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Ultra-narrow superconducting junctions: electromigration to shed light on quantum point contacts
Baumans, Xavier; Cerbu, Dorin; Adami, Obaïd-Allah et al.
2016Applied Superconductivity Conference
 

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Keywords :
Physics; Superconductivity; Nanomaterials
Abstract :
[en] Superconducting nanowires have been, for years now, a topic of great interest due to their potential application in single photon detectors and in quantum computing circuits. In this context, it is of fundamental importance to better understand the undesired and harmful appearance of thermal and quantum fluctuations of the superconducting order parameter [1]-[3] as a function of the wire width. Although superconductors in the mesoscopic regime (i.e. size comparable to ξ and/or λ) have been explored both experimentally and theoretically in depth, the superconducting nanoworld (i.e. at scales of the fermi wavelength) has received much less attention. The lack of experimental results is in part due to the difficulty of sample fabrication, at dimensions beyond the limit reached by conventional lithographic techniques. A promising direction consists of controlling the local displacement of atom by an electron wind, a process known as electromigration (EM) [4] . This effect relies on the combination of local temperature rise and substantial current crowding at nanoconstrictions. While uncontrolled, EM is responsible for the breakdown of small electronic devices, it can be used in a controllable way to further decrease locally the cross section of the nanowire towards single atomic contacts. In this work, we explore in-situ controlled EM to fabricate nano-constrictions immersed in cryogenic environment. We demonstrate that a transition from thermally assisted phase slips (TAPS) to quantum phase slips (QPS) takes place when the effective cross section becomes smaller than ~ 150 nm 2 . In the regime dominated by QPS the nanowire loses completely its capacity to carry current without dissipation, even at the lowest possible temperature [5] . We also demonstrate that the bow-tie shaped constrictions exhibit a negative magnetoresistance at low magnetic fields [5] which can be attributed to the suppression of superconductivity in the contact leads [6] . Strikingly, the detrimental effect caused by the repeated EM can be healed by simply inverting the current direction. These findings reveal the strong potential of the proposed fabrication method to explore various fascinating superconducting phenomena in atomic-size constrictions.
Disciplines :
Physics
Author, co-author :
Baumans, Xavier ;  Université de Liège > Département de physique > Physique expérimentale des matériaux nanostructurés
Cerbu, Dorin;  Katholieke Universiteit Leuven - KUL > Physics and Astronomy > Institute for Nanoscale Physics and Chemistry
Adami, Obaïd-Allah ;  Université de Liège > Département de physique > Département de physique
Zharinov, Vyacheslav;  Katholieke Universiteit Leuven - KUL > Physics and Astronomy > Institute for Nanoscale Physics and Chemistry
Verellen, Niels;  Katholieke Universiteit Leuven - KUL > Physics and Astronomy > Institute for Nanoscale Physics and Chemistry
Papari, Gianpaolo;  Katholieke Universiteit Leuven - KUL > Physics and Astronomy
Scheerder, Jeroen;  Katholieke Universiteit Leuven - KUL > Physics and Astronomy > Institute for Nanoscale Physics and Chemistry
Zhang, Gufei;  Katholieke Universiteit Leuven - KUL > Physics and Astronomy > Institute for Nanoscale Physics and Chemistry
Moshchalkov, Victor;  Katholieke Universiteit Leuven - KUL > Physics and Astronomy > Institute for Nanoscale Physics and Chemistry
Silhanek, Alejandro  ;  Université de Liège > Département de physique > Physique expérimentale des matériaux nanostructurés
Van de Vondel, Joris;  Katholieke Universiteit Leuven - KUL > Physics and Astronomy > Institute for Nanoscale Physics and Chemistry
Language :
English
Title :
Ultra-narrow superconducting junctions: electromigration to shed light on quantum point contacts
Publication date :
06 September 2016
Event name :
Applied Superconductivity Conference
Event date :
04/09/2016-09/09/2016
Audience :
International
Funders :
ULiège - Université de Liège [BE]
Available on ORBi :
since 21 September 2016

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