Flux penetration in a superconducting strip with an edge indentation

Vestgården, Jørn Inge; Shantsev, D. V.; Galperin, Y. M.; Johansen, T. H.

doi:10.1103/physrevb.76.174509

Cited by 19 publications

(35 citation statements)

References 23 publications

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“…The large electric fields and the larger traffic of vortices at the border defects should cause the indentations to be preferred nucleation spots for the development of thermomagnetic instabilities [35]. In contrast to that expectation, we do not observe a more frequent occurrence of thermal flux avalanches at the indentations, but rather the opposite (i.e., avalanches avoid the indentation), confirming a recent experimental report [24].…”

Section: Magnetic Imaging Of Flux Penetrationcontrasting

confidence: 56%

“…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%

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

et al. 2017

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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.

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Section: Magnetic Imaging Of Flux Penetrationcontrasting

confidence: 56%

Section: Magnetic Imaging Of Flux Penetrationmentioning

confidence: 99%

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

et al. 2017

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“…An additional consequence of border defects is that flux penetrates deeper into the sample, by an amount ∆, as compared to the penetration without indentations. 4 In the framework of the Bean critical state model applicable to bulk superconducting samples without demagnetization effects, a circular cavity of radius R, where the density of current j = 0, positioned close to the sample's edge should give rise to a parabolic d-line determined by the equation 3,5,6 y(…”

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confidence: 99%

Magnetic flux penetration in Nb superconducting films with lithographically defined microindentations

et al. 2016

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We present a thorough investigation by magneto-optical imaging of the magnetic flux penetration in Nb thin films with lithographically defined border indentations. We demonstrate that discontinuity lines (d-lines), caused by the abrupt bending of current streamlines around the indentations, depart from the expected parabolic trend close to the defect and depend on the shape and size of the indentation as well as on the temperature. These findings are backed up and compared with theoretical results obtained by numerical simulations and analytical calculations highlighting the key role played by demagnetization effects and the creep exponent n. In addition, we show that the presence of nearby indentations and submicrometer random roughness of the sample border can severely modify the flux front topology and dynamics. Strikingly, in contrast to what has been repeatedly predicted in the literature, we do not observe that indentations act as nucleation spots for flux avalanches, but they instead help to release the flux pressure and avoid thermomagnetic instabilities.

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“…26 Nevertheless, the exact nucleation site of the next dendrite, the field interval between two consecutive events, and the final shape of the dendritic structure are nonreproducible. To illustrate this, Fig.…”

Section: Dendritic Flux Avalanchesmentioning

confidence: 99%

Dendritic flux avalanches in superconducting films

Yurchenko

Johansen

Galperin

2009

Low Temperature Physics

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Thermomagnetic instability in general, and dendritic flux avalanches in particular, have attracted considerable attention of both scientists and engineers working on superconductor applications. Though being harmful for the performance of many superconducting devices, the avalanches provide a fruitful playground for experimental and theoretical studies of complex dynamics of the vortex matter. In this paper we report on the progress in understanding the mechanisms responsible for the development of the giant magnetic avalanches. We review recent results on magneto-optical imaging of the fingering instability in superconducting films and analyze them on the basis of recent theoretical model that establishes criteria for onset of the dendritic avalanches.

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Flux penetration in a superconducting strip with an edge indentation

Cited by 19 publications

References 23 publications

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

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

Magnetic flux penetration in Nb superconducting films with lithographically defined microindentations

Dendritic flux avalanches in superconducting films

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