What is the best gate for vortex entry into type-II superconductor?

Aladyshkin, A. Yu.; Mel’nikov, A. S.; Shereshevsky, I. A.; Tokman, I. D.

doi:10.1016/s0921-4534(01)00288-x

Cited by 27 publications

(14 citation statements)

References 12 publications

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“…In addition to linear stability analysis, previous work has also used the time-dependent theory to estimate the entry field [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] . An advantage of using the timedependent theory, is the ability to explore rough geometries.…”

Section: A Agreement With Previous Workmentioning

confidence: 99%

“…Often real systems have rough surfaces and interior defects that don't match this geometry. The role of surface roughness on H sh in two dimensional geometries with surface defects has been studied extensively within Ginzburg-Landau theory [15][16][17][18] . There has also been considerable effort to simulate vortex nucleation and subsequent dynamics for more complicated domains within time-dependent Ginzburg-Landau (TDGL) theory [19][20][21][22][23][24][25][26][27][28][29] .…”

Section: Introductionmentioning

confidence: 99%

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Vortex nucleation in superconductors within time-dependent Ginzburg-Landau theory in two and three dimensions: Role of surface defects and material inhomogeneities

et al. 2020

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We use Time-Dependent Ginzburg-Landau theory to study the nucleation of vortices in type II superconductors in the presence of both geometric and material inhomogeneities. The superconducting Meissner state is meta-stable up to a critical magnetic field, known as the superheating field. For a uniform surface and homogenous material, the superheating transition is driven by a non-local critical mode in which an array of vortices simultaneously penetrate the surface. In contrast, we show that even a small amount of disorder localizes the critical mode and can have a significant reduction in the effective superheating field for a particular sample. Vortices can be nucleated by either surface roughness or local variations in material parameters, such as Tc. Our approach uses a finite element method to simulate a cylindrical geometry in 2 dimensions and a film geometry in 2 and 3 dimensions. We combine saddle node bifurcation analysis along with a novel fitting procedure to evaluate the superheating field and identify the unstable mode. We demonstrate agreement with previous results for homogenous geometries and surface roughness and extend the analysis to include variations in material properties. Finally, we show that in three dimensions, suface divots not aligned with the applied field can increase the super heating field. We discuss implications for fabrication and performance of superconducting resonant frequency cavities in particle accelerators.

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Section: A Agreement With Previous Workmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Vortex nucleation in superconductors within time-dependent Ginzburg-Landau theory in two and three dimensions: Role of surface defects and material inhomogeneities

et al. 2020

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“…Nonuniformity may come from the Meissner (screening) effect which is important in wide films/bridges with width w > λ 2 /d (λ is the London penetration depth, d is the thickness of the film/bridge). In narrow films/bridges (w λ 2 /d) spatially nonuniform current distribution may arise due to the current crowding effect near edge/surface irregularities [12][13][14] or due to specific geometry [15]. We demonstrate, that for not very wide bridges and currents close to I c , the delay in the voltage response is mainly connected with the entrance of the first vortex and qualitatively resembles the time delay of quasi-onedimensional (1D) bridges.…”

Section: Introductionmentioning

confidence: 73%

“…Note that all previous theories predicted a strong temperature dependence of t d near T c [2,3] due to the coefficient a(T ) in Eq. (13). In Ref.…”

Section: Discussionmentioning

confidence: 99%

Temporary cooling of quasiparticles and delay in voltage response of superconducting bridges after abruptly switching on the supercritical current

Vodolazov

Peeters

2014

Phys. Rev. B

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We revisit the problem of the dynamic response of a superconducting bridge after abruptly switching on the supercritical current. In contrast to previous theoretical works we take into account spatial gradients and use both the local temperature approach and the kinetic equation for the distribution function of quasiparticles. We find that the temperature dependence of the finite delay time t d in the voltage response is model dependent and relatively large t d is connected with temporary cooling of quasiparticles during decay of superconducting order parameter | | in time. It turns out that the presence of even small inhomogeneities in the bridge or finite length of the homogenous bridge favors a local suppression of | | during the dynamic response. It results in a decrease of the delay time, in comparison with the spatially uniform model, due to the diffusion of nonequilibrium quasiparticles from the region with locally suppressed | |. In the case when the current density is maximal near the edge of a not very wide bridge the delay time is mainly connected with the time needed for the nucleation (entrance) of the first vortex and t d could be tuned by a weak external magnetic field. We also find that a short alternating current pulse (sinusoidlike) with zero time average may result in a nonzero time-averaged voltage response where its sign depends on the phase of the ac current.

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“…We use Fourier's law to determine the coefficients a, c and e in Eqs. ( 7) and (10). For 0 ≤ r ≤ D, Q = P GB /D 2 , so that:…”

Section: −κ Nb3snmentioning

confidence: 99%

Analysis of Magnetic Vortex Dissipation in Sn-Segregated Boundaries in Nb$_3$Sn Superconducting RF Cavities

Carlson,

Pack,

Transtrum

et al. 2020

Preprint

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We study mechanisms of vortex nucleation in Nb3Sn SRF cavities using a combination of experimental, theoretical, and computational methods. Scanning transmission electron microscopy (STEM) image and energy dispersive spectroscopy (EDS) of some Nb3Sn cavities show Sn segregation at grain boundaries in Nb3Sn with Sn concentration as high as ∼35 at.% and widths ∼3 nm in chemical composition. Using ab initio calculations, we estimate the effect excess tin has on the local superconducting properties of the material. We model Sn segregation as a lowering of the local critical temperature. We then use time-dependent Ginzburg-Landau theory to understand the role of segregation on magnetic vortex nucleation. Our simulations indicate that the grain boundaries act as both nucleation sites for vortex penetration and pinning sites for vortices after nucleation. Depending on the magnitude of the applied field, vortices may remain pinned in the grain boundary or penetrate the grain itself. We estimate the superconducting losses due to vortices filling grain boundaries and compare with observed performance degradation with higher magnetic fields. We estimate that the quality factor may decrease by an order of magnitude (10 10 to 10 9 ) at typical operating fields if 0.03% of the grain boundaries actively nucleate vortices. We additionally estimate the volume that would need to be filled with vortices to match experimental observations of cavity heating.

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What is the best gate for vortex entry into type-II superconductor?

Cited by 27 publications

References 12 publications

Vortex nucleation in superconductors within time-dependent Ginzburg-Landau theory in two and three dimensions: Role of surface defects and material inhomogeneities

Vortex nucleation in superconductors within time-dependent Ginzburg-Landau theory in two and three dimensions: Role of surface defects and material inhomogeneities

Temporary cooling of quasiparticles and delay in voltage response of superconducting bridges after abruptly switching on the supercritical current

Analysis of Magnetic Vortex Dissipation in Sn-Segregated Boundaries in Nb$_3$Sn Superconducting RF Cavities

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