Vortex ratchet induced by controlled edge roughness

Cerbu, Dorin; Gladilin, Valadimir N.; Cuppens, J.; Fritzsche, Joachim; Tempere, J.; Devreese, Jozef T.; Moshchalkov, Victor; Silhanek, Alejandro; Vondel, J. Van de

doi:10.1088/1367-2630/15/6/063022

Cited by 40 publications

(36 citation statements)

References 39 publications

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“…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

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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 Penetrationmentioning

confidence: 99%

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

et al. 2017

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“…Recent reports have shown that crowding of Meissner currents can severely affect the conditions for vortex entry in sharp-bends 10,[30][31][32][33] . Within this scenario, border indentations of different shapes lead to different suppressions of the flux entry barrier.…”

Section: 29mentioning

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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“…In order to achieve this goal, a careful sample design and fabrication are necessary. First, the presence of surface defects may create spots for premature entry of vortices, 4,15,16 thus influencing the study of the intrinsic mechanisms. Second, in thin-film geometry, vortices will move to the center of the sample as soon as they nucleate, 17 making it impossible to experimentally observe their entry.…”

Section: Thatmentioning

confidence: 99%

First vortex entry into a perpendicularly magnetized superconducting thin film

et al. 2013

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In type-II superconductors, the flux-free state (Meissner state) may be invaded by vortices bearing quantized flux once H is above the lower critical field H c1 . However, the actual first flux penetration does not occur at H c1 due to the presence of a surface barrier and the fact that the Meissner state may also exist as a metastable state up to a larger (superheating) field. In this work we determine the field for the first vortex penetration in superconductors by directly imaging the first vortex threading a superconducting Pb film with antidots. We find that the first vortex penetration occurs when the surface superconducting currents reach the depairing current, locally breaking superconductivity and allowing a vortex to nucleate.

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Vortex ratchet induced by controlled edge roughness

Cited by 40 publications

References 39 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

First vortex entry into a perpendicularly magnetized superconducting thin film

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