Critical current from surface barriers in type-II superconducting strips

Benkraouda, Maamar; Clem, John R.

doi:10.1103/physrevb.58.15103

Cited by 85 publications

(107 citation statements)

References 21 publications

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“…[6,10]. The virgin curve of the irreversible M (H a ) of strips and disks at small H a coincides with the ideal Meissner straight line M = −H a /(1 − N ) of the corresponding ellipsoid, Eqs.…”

Section: Pin-free Superconductorsmentioning

confidence: 99%

Superconductors in realistic geometries: geometric edge barrier versus pinning

Brandt

2000

Physica C: Superconductivity

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Section: Pin-free Superconductorsmentioning

confidence: 99%

Superconductors in realistic geometries: geometric edge barrier versus pinning

Brandt

2000

Physica C: Superconductivity

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“…In this regime, there are no vortices present in the strip for I < I c , while larger currents result in a dynamical flux flow state with vortices entering the strip at one edge and moving across to the other edge. For larger H a , the external field can be sufficient to push vortices into the strip, even for I = 0, and these vortices arrange in a static dome-shaped structure in the middle of the strip [14,15]. When I = 0, the dome shifts towards one edge and I c is reached when the self-field plus H a at the opposite edge overcome the entry barrier to allow new vortices to enter.…”

mentioning

confidence: 99%

Asymmetric weak-pinning superconducting channels: Vortex ratchets

Heitmann

Song

et al. 2007

Phys. Rev. B

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The controlled motion of objects through narrow channels is important in many fields. We have fabricated asymmetric weak-pinning channels in a superconducting thin-film strip for controlling the dynamics of vortices. The lack of pinning allows the vortices to move through the channels with the dominant interaction determined by the shape of the channel walls. We present measurements of vortex dynamics in the channels and compare these with similar measurements on a set of uniformwidth channels. While the uniform-width channels exhibit a symmetric response for both directions through the channel, the vortex motion through the asymmetric channels is quite different, with substantial asymmetries in both the static depinning and dynamic flux flow. This vortex ratchet effect has a rich dependence on magnetic field and driving force amplitude.PACS numbers: 74.25. Qt, 74.25.Sv, 74.25.Op Recently there has been much interest in developing artificial ratchets for generating directed motion using tailored asymmetries [1]. Such ratchets could be used as pathways for producing net transport of matter at the nanoscale. In addition, artificial ratchets can serve as model systems for understanding similar ratchet phenomena in biological systems while allowing for experimental control over many of the ratchet parameters [2]. A variety of ratchets have been considered, but one particular type that has been implemented in several different systems is the rocking ratchet, where a spatial asymmetry is engineered into the potential energy landscape governing particle motion and an external control variable can be adjusted to tilt this potential. The application of an oscillatory drive of the control variable with zero mean can result in the net motion of particles through the potential because of the different rates for overcoming the barriers in the two directions through the ratchet.Implementations of ratchets in solid-state devices include asymmetric structures of electrostatic gates above a two-dimensional electron gas [3], and arrays of Josephson junctions with asymmetric critical currents [4]. Structures have also been developed for producing a ratchet effect with vortices in superconducting thin films involving either asymmetric arrangements of pinning centers [5,6] or asymmetric magnetic pinning structures [7]. In this Communication, we describe a vortex ratchet using two-dimensional guides to generate asymmetric channels for vortex motion. In our structures, the potential asymmetries arise from differences in the interaction strength between vortices and the channel walls, resulting in a substantial ratchet effect for the motion of vortices through the channels. Our design is related to a previous vortex ratchet proposal [8], although our ratchet is in a somewhat different parameter regime.Nanoscale channels for guiding vortices through superconducting films with a minimal influence from pin- ning have been developed for studies of vortex matter in confined geometries, including experiments on melting [9], commensurabili...

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“…The nature of the edge barrier itself ͑Bean-Livingston, 3,4 geometrical, [5][6][7] or enhanced bulk pinning at the edges 8,9 ͒ does not matter. In what follows, we imply a most robust geometrical barrier.…”

Section: Introductionmentioning

confidence: 99%

Overcritical states of a superconductor strip in a magnetic environment

2000

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A current-carrying superconducting strip partly penetrated by magnetic flux and surrounded by a bulk magnet of high permeability is considered. Two types of samples are studied: those with critical current controlled by an edge barrier dominating over the pinning, and those with high pinning-mediated critical current masking the edge barrier. It is shown for both cases that the current distribution in a central flux-free part of the strip is strongly affected by the actual shape of the magnetic surroundings. Explicit analytical solutions for the sheet current and self-field distributions are obtained which show that, depending on the geometry, the effect may suppress the total loss-free transport current of the strip or enhance it by orders of magnitude. The effect depends strongly on the shape of the magnet and its distance to the superconductor but only weakly on the magnetic permeability.

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Critical current from surface barriers in type-II superconducting strips

Cited by 85 publications

References 21 publications

Superconductors in realistic geometries: geometric edge barrier versus pinning

Superconductors in realistic geometries: geometric edge barrier versus pinning

Asymmetric weak-pinning superconducting channels: Vortex ratchets

Overcritical states of a superconductor strip in a magnetic environment

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