[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
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