Controllable morphology of flux avalanches in microstructured superconductors

Motta, M.; Colauto, F.; Vestgården, Jørn Inge; Fritzsche, Joachim; Timmermans, Matias; Cuppens, J.; Attanasio, C.; Cirillo, C.; Moshchalkov, Victor; Vondel, J. Van de; Johansen, T. H.; Ortiz, W.A.; Silhanek, Alejandro

doi:10.1103/physrevb.89.134508

Cited by 45 publications

(47 citation statements)

References 35 publications

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“…(ii) The high value of λ (∼500 nm), compared to the dimensions of the nanoisland, ensuring demagnetization effects will not play a role [18]. (iii) The small value of ξ (∼6 nm) makes it possible to visualize spatial modulations in the superconducting condensate using STM [18]. All aforementioned ingredients allow a direct comparison with the theoretical models used to describe these systems [4,19].…”

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“…As such, the vortex-vortex and vortex-boundary interactions will play a dominant role [17]. (ii) The high value of λ (∼500 nm), compared to the dimensions of the nanoisland, ensuring demagnetization effects will not play a role [18]. (iii) The small value of ξ (∼6 nm) makes it possible to visualize spatial modulations in the superconducting condensate using STM [18].…”

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Direct observation of condensate and vortex confinement in nanostructured superconductors

et al. 2016

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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...

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Direct observation of condensate and vortex confinement in nanostructured superconductors

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“…25 However, this kind of catastrophic event in amorphous plain films of Mo 79 Ge 21 was not reported so far. The lower panels of Figure 1 show representative examples of such avalanches in three a-Mo 79 Ge 21 films.…”

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Enhanced pinning in superconducting thin films with graded pinning landscapes

Motta

Colauto

Ortiz

et al. 2013

Applied Physics Letters

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A graded distribution of pinning centers (antidots) in superconducting MoGe thin films has been investigated by magnetization and magneto-optical imaging. The pinning landscape has maximum density at the border, decreasing progressively towards the center. At high temperatures and low fields, where this landscape mimics the vortex distribution predicted by the Bean model, an increase of the critical current is observed. At low temperatures and fields, the superconducting performance of the non-uniform sample is also improved due to suppression of thermomagnetic avalanches. These findings emphasize the relevance of non-uniform pinning landscapes, so far experimentally unexplored, on the enhancement of pinning efficiency.

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“…In our experiments, these would correspond to the presence of particularly pronounced defects at the superconducting film boundary, responsible for preferential flux penetration [32]. The question of whether these are linked to avalanche-like flux penetration at a low temperature [32,34,35,[47][48][49][50][51] remains to be established. Simulations in [23] reveal that the low-distance regime (x < l × ) corresponds to multi-affine behavior, arising from the superposition of growth fronts initiated by different rare events, while the regime of intermediate lengths l × < x < l sat signals the return to a self-affine front determined by the progression of vortices through bulk disorder.…”

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Edge Contamination, Bulk Disorder, Flux Front Roughening, and Multiscaling in Type II Superconducting Thin Films

et al. 2017

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Abstract:We have investigated the effect of different types of disorder on the propagation, roughness, and scaling properties of magnetic flux fronts in a type II superconductor. A progression from the usual (Kardar-Parisi-Zhang-type) scaling to multiscaling is observed as the disorder strength is increased. A hierarchy of disorder strengths is established for YBa 2 Cu 3 O 7−δ thin films. The results cast light on the physical origin of the roughening of flux fronts, and they are of interest for the design and elimination of flux noise in microscopic superconducting thin-film devices.

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Controllable morphology of flux avalanches in microstructured superconductors

Cited by 45 publications

References 35 publications

Direct observation of condensate and vortex confinement in nanostructured superconductors

Direct observation of condensate and vortex confinement in nanostructured superconductors

Enhanced pinning in superconducting thin films with graded pinning landscapes

Edge Contamination, Bulk Disorder, Flux Front Roughening, and Multiscaling in Type II Superconducting Thin Films

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