Flux Line Shear Studied in Sputtered NbN Films

Pruymboom, A.; Hoondert, W.H.B.; Zandbergen, H.W.; Kes, P.H.

doi:10.7567/jjaps.26s3.1529

Cited by 11 publications

(4 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The visualization identifies flux flow by highly distorted fluxons past ͑almost͒ stationary fluxons in the grains with almost no hexagonal symmetry as the mechanism that determines J C in polycrystalline materials. Flux flow along grain boundaries past an ordered hexagonal FLL has been proposed before [2][3][4] but the visualization shows the following: the fluxons that move along grain boundaries are strongly distorted ͑i.e., not circular͒ particularly at the grain boundary triple points; the order parameter is strongly depressed along all the grain boundaries; there is a wide fluxon-free layer next to the grain boundaries along which a large current flows; the fluxons within the grains are almost stationary and their arrangement or order is strongly affected by the shape of the grains rather than having hexagonal symmetry. Hence, this work provides the means to identify the important characteristics or approximations that can be used to reliably explain the Kramer functional form.…”

mentioning

confidence: 99%

“…However, the forces add together in a manner so complex that there is no reliable description of the flux-line lattice ͑FLL͒ at criticality or which fluxons move within the superconductor during dissipation. The lack of theoretical understanding is exemplified by the widespread use of both flux-shear models [1][2][3][4] and flux-pinning models. 4,5 In fluxshear models, some fluxons are strongly pinned so that dissipation first occurs when unpinned fluxons overcome the fluxon-fluxon forces and shear past the stationary ones.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Visualizing the mechanism that determines the critical current density in polycrystalline superconductors using time-dependent Ginzburg-Landau theory

Carty

Hampshire

2008

Phys. Rev. B

View full text Add to dashboard Cite

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details.

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

Visualizing the mechanism that determines the critical current density in polycrystalline superconductors using time-dependent Ginzburg-Landau theory

Carty

Hampshire

2008

Phys. Rev. B

View full text Add to dashboard Cite

show abstract

“…7 In strongly pinning NbN with a T c of 11 K and a B c2 at 4.2 K of about 8.8 T, J c is at least two orders of magnitude higher. 8 For amorphous films, spectroscopic imaging is feasible because of the very flat surface characteristics. However, even a small amount of oxidation is detrimental to mapping the superconducting gap, which is the way to determine vortex core positions.…”

Section: Imaging Of Vortex Configurations In Thin Films By Scanning-tmentioning

confidence: 99%

Imaging of vortex configurations in thin films by scanning-tunneling microscopy

Baarle

Troianovski

Nishizaki

et al. 2003

Applied Physics Letters

Self Cite

View full text Add to dashboard Cite

We report on imaging of vortices in thin superconducting films using surface passivation with an ultrathin Au layer. This allows investigation of surfaces that oxidize easily, as well as the mounting of samples in air. We studied vortex configurations in a material with weak vortex pinning (a-Mo2.7Ge) and a strongly pinning material (NbN) at 4.2 K in magnetic fields up to 1.4 T. In a-Mo2.7Ge, we observe a well-ordered hexagonal lattice, with local defects beginning to appear around 1.0 T. In NbN, the vortex lattice is fully disordered.

show abstract

“…Similar results have been obtained for the pinning force density in polycrystalline NbN films. 24 As pointed out in Ref. 15, this field dependence of the threshold depinning force can be explained in terms of vortex channels flowing past regions of vortices trapped by pinning centers.…”

Section: Rapid Communicationsmentioning

confidence: 94%

Direct evidence for filamentary and channel vortex flow in Pb/In superconducting films

1999

View full text Add to dashboard Cite

Filamentary vortex flow in thin Pb/͑14 at. %͒In films is revealed by multiple voltage jumps in currentvoltage (IV) characteristics below a critical magnetic field much lower than the upper critical field B c2 . The voltage jumps exhibit large counterclockwise hysteresis which diminishes with increasing field leading to bistable behavior close to the onset of free-flux flow. From the magnetic field and temperature dependence of the jump heights and currents at which jumps occur we infer that the number of flux lines in each channel or filament remains constant. In this regime, where the shear modulus of the vortex lattice is negligible, we find a nearly parabolic dependence of the depinning force on magnetic field, which is a signature of channel vortex motion. ͓S0163-1829͑99͒50710-8͔The vortex dynamics in type-II superconductors has received much attention partly due to its importance for the technological issue of superconductivity breakdown under a transport current, but also because its study has largely contributed to understanding disorder-driven effects on the vortex lattice. The influence of disorder potential on collective effects due to lattice pinning also plays a crucial role in related areas like Wigner-crystal formation in electron gases 1 and charge-density wave propagation. 2 In high-T c superconducting materials, phenomena such as vortex-lattice melting and the transition to a glass phase appear as a consequence of the interplay between the peculiar vortex-vortex interaction and the pinning mechanism. 3-7 Investigations of the effect of pinning on the vortex lattice as well as on vortex motion [8][9][10][11] have shown that the flux-flow behavior can be divided into two distinct regimes: elastic flow, where disorder is weak and the vortex structure essentially moves as a whole, and plastic flow with strong disorder, where the vortex lattice can be torn. The onset of vortex motion in the two regimes can differ substantially in that for plastic flow, vortices can flow in filaments or channels with the rest of the structure remaining pinned. 12,13 A model for vortex flow in the form of filaments and channels has been proposed recently 14-16 for interpreting experimental results of studies concerning the tearing of the vortex lattice 12 and the current induced transition from plastic to elastic vortex flow. 17 Time integration of the equation of motion as well as Monte Carlo techniques were applied to simulate filamentary flow of vortices and the resulting current-voltage (IV) characteristics. Furthermore, discontinuities in IV curves of 2H-NbSe 2 have been observed, 18 which were tentatively ascribed to vortex flow in channels. The channel flow state was found to be metastable and subject to strong history effects. Recently, Matsuda et al. 19 showed motion picture recordings of flowing vortices, where depinning processes of single-row vortex structures and subsequent filamentary and channel motion can clearly be seen.In this paper we report clear evidence for filamentary and channel-vortex flow, wh...

show abstract

Flux Line Shear Studied in Sputtered NbN Films

Abstract: It is shown that above B≈0.5Bc2, the critical current density of sputtered NBN films is limited by flux line shear.The channel width for shear is determined by the lattice spacing rather than by the grain size.

Cited by 11 publications

References 0 publications

Visualizing the mechanism that determines the critical current density in polycrystalline superconductors using time-dependent Ginzburg-Landau theory

Visualizing the mechanism that determines the critical current density in polycrystalline superconductors using time-dependent Ginzburg-Landau theory

Imaging of vortex configurations in thin films by scanning-tunneling microscopy

Direct evidence for filamentary and channel vortex flow in Pb/In superconducting films

Contact Info

Product

Resources

About