Current crowding effects in superconducting corner-shaped Al microstrips

Adami, O.-A.; Cerbu, Dorin; Cabosart, Damien; Motta, M.; Cuppens, J.; Ortiz, W.A.; Moshchalkov, Victor; Hackens, Benoît; Delamare, Romain; Vondel, J. Van de; Silhanek, Alejandro

doi:10.1063/1.4790625

Cited by 53 publications

(43 citation statements)

References 18 publications

(21 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Indeed, previous theoretical calculations, regarding the impact of defects on the depletion are in very good agreement with our observations [26]. As a result, this is the first direct observation of the current crowding effect at the nanoscale [27,28]. In order to strengthen our claim we also present the ZBC maps at 60 mT.…”

supporting

confidence: 76%

Direct observation of condensate and vortex confinement in nanostructured superconductors

et al. 2016

Self Cite

View full text Add to dashboard Cite

In this work we report a scanning tunneling microscopy investigation of lithographically defined superconducting nanosquares. The obtained spectroscopic maps reveal the spatial evolution of both the superconducting condensate and the screening currents as a function of the applied magnetic field. The symmetry of the nanostructure is imposed on the condensate and it controls the distribution of the vortices inside the nanosquare. Our local study allows exploring the impact of small structural defects, omnipresent in these kind of structures, on both the supercurrent and vortex distribution. As a result, direct experimental evidence of vortex pinning and current crowding at the nanoscale has been obtained. DOI: 10.1103/PhysRevB.93.054514 Confinement effects play an important role in different physical phenomena especially in quantum systems like Bose-Einstein condensates, superconductors, and superfluids. For example, the ability to structure superconducting devices at length scales comparable to the characteristic sizes (penetration dept λ and coherence length ξ ) of the condensate revealed a vast world of possibilities to explore quantum phenomena (e.g., creation of artificial atoms [1], induction of quantum phase slip lines [2], confinement effects [3], to name a few). In the latter example, theoretical modeling of these systems solving the Ginzburg-Landau (G-L) [4,5] or Bogoliubov-deGennes (B-dG) [6] equations for single and/or multiband mesoscopic superconductors has been done. All these simulations unveil the importance of confinement in mesoscopic superconducting systems. For example, the symmetry of the nanostructure will compete with the vortex-vortex interaction resulting in different vortex configurations compared to the triangular Abrikosov lattice, found in bulk superconductors [3][4][5][6].These intriguing effects were experimentally investigated, using low temperature transport measurements, by probing the influence of nanostructuring on the superconductor/normal phase boundary [3]. Although these measurements proved the importance of size and shape they do not give sufficient local information about the spatial distribution of the superconducting condensate. Moreover, a different approach is needed to explore the condensate in the nondissipative (zero voltage) state. In order to tackle these issues a second set of experiments probes the magnetic field profiles, generated by the superconducting currents, by using magnetic field sensitive probes (e.g., Hall probe [7,8], scanning Hall probe microscopy [9], Bitter decoration [10], and scanning SQUID microscopy [11]). These techniques indeed visualized the symmetry-induced vortex configurations in superconducting nanostructures within the low confinement regime (i.e., nanostructure size ∼λ ξ ). The observed configurations are the results of the imposed boundary conditions and the repulsive magnetic interactions between vortices. In the strong confinement regime (i.e., nanostructure size ∼ξ λ), the distribution of the superconducting condensate is gov...

show abstract

supporting

confidence: 76%

Direct observation of condensate and vortex confinement in nanostructured superconductors

et al. 2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…Further increase of B above B max will lead to a decrease of the measured I c , compare to figure 3(a). This effect of a reduction of the current crowding effect by an externally applied magnetic field has been predicted theoretically [36] and confirmed experimentally in Al microstrips near T c [39] and in Nb, NbN and TaN sub-micrometer bent strips at T T c [32]. The increase of j c with increasing B is not described by (1) anymore, but follows the dependence [36] …”

Section: Stationary State Of Snspdmentioning

confidence: 77%

Detection mechanism of superconducting nanowire single-photon detectors

Engel¹,

Renema²,

Ilin³

et al. 2015

Supercond. Sci. Technol.

137

108

View full text Add to dashboard Cite

Abstract. In this paper we intend to give a comprehensive description of the current understanding of the detection mechanism in superconducting nanowire singlephoton detectors. We will review key experimental results related to the detection mechanism, e.g. the variations of the detection probability as a function of bias current, temperature or magnetic field. Commonly used detection models will be introduced and we will analyze their predictions in view of the experimental observations. Although none of the proposed detection models is able to describe all experimental data, it is becoming increasingly clear that vortices are essential for the formation of the initial normal-conducting domain that triggers a detection event.

show abstract

“…2, the indentations act as flux faucets as a consequence of a combined effect of current crowding and the formation of parabolic discontinuity lines [24]. At low fields, when the sample is in the Meissner state, screening currents running around the sample perimeter are forced to circumvent the triangular indentations, leading to an increase of the streamline density at the vertices of the indentations [31][32][33][34][35][36]. This locally higher current density favors the penetration of flux quanta through this particular point of the structure.…”

Section: Magnetic Imaging Of Flux Penetrationmentioning

confidence: 99%

Flux penetration in a superconducting film partially capped with a conducting layer

et al. 2017

Self Cite

View full text Add to dashboard Cite

The influence of a conducting layer on the magnetic flux penetration in a superconducting Nb film is studied by magneto-optical imaging. The metallic layer partially covering the superconductor provides an additional velocity-dependent damping mechanism for the flux motion that helps to protect the superconducting state when thermomagnetic instabilities develop. If the flux advances with a velocity slower than w = 2/μ 0 σ t, where σ is the cap layer conductivity and t is its thickness, the flux penetration remains unaffected, whereas for incoming flux moving faster than w, the metallic layer becomes an active screening shield. When the metallic layer is replaced by a perfect conductor, it is expected that the flux braking effect will occur for all flux velocities. We investigate this effect by studying Nb samples with a thickness step. Some of the observed features, namely the deflection of the flux trajectories at the border of the thick center, as well as the favored flux penetration at the indentation, are reproduced by time-dependent Ginzburg-Landau simulations.

show abstract

Current crowding effects in superconducting corner-shaped Al microstrips

Cited by 53 publications

References 18 publications

Direct observation of condensate and vortex confinement in nanostructured superconductors

Direct observation of condensate and vortex confinement in nanostructured superconductors

Detection mechanism of superconducting nanowire single-photon detectors

Flux penetration in a superconducting film partially capped with a conducting layer

Contact Info

Product

Resources

About