Flux vortices and transport currents in type II superconductors

Multi-quanta, or giant, vortices (GVs) are known to appear in very small superconductors near the superconducting transition due to strong confinement of magnetic flux. Here we present evidence for a new, pinning-related, mechanism for the formation of GVs. Using Bitter decoration to visualise vortices in small Nb disks, we show that confinement in combination with strong disorder causes individual vortices to merge into clusters or even GVs well below T c and H c2 , in contrast to well-defined shells of individual vortices found in the absence of pinning.Mesoscopic superconductors, i.e., such that they can accommodate only a small number of vortices, are known to exhibit complex and unique vortex structures due to the competition between surface superconductivity and vortex-vortex interactions [see e.g. 1-6]. For mesoscopic disks, theoretical studies found two kinds of superconducting states: a giant vortex (GV), i.e., a circular symmetric state with a fixed value of angular momentum that can carry several flux quanta [1,2] and multivortex states (MVS) with an effective total angular momentum corresponding to the number of vortices in the disk (vorticity L) [3]. Recently, it became possible to experimentally distinguish between a singlecore GV and a MVS composed of singly quantized vortices using the multiple-small-tunnel-junction

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“…3(d)). We note that the above pinning forces are of the same order of magnitude as those estimated for normal inclusions in Nb of radius ≥ξ [19].…”

supporting

confidence: 61%

Pinning-Induced Formation of Vortex Clusters and Giant Vortices in Mesoscopic Superconducting Disks

et al. 2007

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“…Currents flowing parallel the in-plane vortices do not impose any force on them and could reach the depairing current value before any dissipation occurs. In fact, experiments on current-carrying superconducting wires in the presence of a longitudinal field showed an enhancement of the critical current [11]. However, the dissipation still occurred well below the depairing current density.…”

Section: Introductionmentioning

confidence: 99%

“…The idea of flux cutting was first introduced [11,52] to explain unexpected voltage oscillations in current carrying SC wires in the axial magnetic field. Since then, the force free configurations and transverse vortex motion in longitudinal currents were addressed in many theoretical works but still remain a hypothetical concept.…”

Section: Flux Cuttingmentioning

confidence: 99%

“…The counter-motion and crossing of helices with different pitch and chirality induce cutting and reconnection of vortices into new helices. This negates flux pumping and instead introduces measurable voltage oscillations along the wire [11]. Although estimates of the currents resulting in the helical instability in [12] were too small, the flux cutting scenario was widely accepted, further developed, and is still considered in various modern models of the critical state [13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

“…However, the dissipation still occurred well below the depairing current density. This was associated with appearance of helical vortex instabilities that emerge when the self-field of the transport current in the SC wire generates vortex helices on the surface, which are then pushed to the center of the wire by the current induced Lorentz force [11].…”

Section: Introductionmentioning

confidence: 99%

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Flux cutting in high-Tcsuperconductors

et al. 2015

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We performed magneto-optical study of flux distributions in a YBCO crystal under various applied crossed-field orientations to elucidate the complex nature of magnetic flux cutting in superconductors. Our study reveals unusual vortex patterns induced by the interplay between flux-cutting and vortex pinning. We observe strong flux penetration anisotropy of the normal flux B ⊥ in the presence of an in-plane field H || and associate the modified flux dynamics with staircase structure of tilted vortices in YBCO and the flux-cutting process.We demonstrate that flux-cutting can effectively delay vortex entry in the direction transverse to H || . Finally, we elucidate details of the vortex-cutting and reconnection process using time-dependent Ginzburg-Landau simulations.

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The Influence of Nano-SiC on the Flux Pinning of YBa2Cu3O7—y/Nano-SiC Composites

Yang

Zhang

et al. 1998

phys. stat. sol. (a)

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Flux vortices and transport currents in type II superconductors

Cited by 1,590 publications

References 213 publications

Pinning-Induced Formation of Vortex Clusters and Giant Vortices in Mesoscopic Superconducting Disks

Pinning-Induced Formation of Vortex Clusters and Giant Vortices in Mesoscopic Superconducting Disks

Flux cutting in high-Tcsuperconductors

The Influence of Nano-SiC on the Flux Pinning of YBa2Cu3O7—y/Nano-SiC Composites

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