Impact of edge-barrier pinning in superconducting thin films

Jones, Wesley A.; Barnes, Paul N.; Mullins, M. J.; Baca, F. J.; Emergo, R. L. S.; Wu, Judy; Haugan, Timothy J.; Clem, John R.

doi:10.1063/1.3529945

Cited by 18 publications

(17 citation statements)

References 25 publications

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“…45 However, edge pinning has been shown to play an increasingly dominant role in measurements using narrow strips or bridges (width <10 μm) to assure that the current supply is adequate to do the measurements. 46,47 The theoretical calculations in the present paper are intended to apply to even thinner and narrower superconducting strips (thickness ∼5 nm, width ∼50-200 nm). In such films, vortices introduced into the strip by a large applied perpendicular magnetic field 24 presumably can be pinned by bulk pinning sites.…”

Section: Discussionmentioning

confidence: 99%

Geometry-dependent critical currents in superconducting nanocircuits

2011

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In this paper, we calculate the critical currents in thin superconducting strips with sharp right-angle turns, 180• turnarounds, and more complicated geometries, where all the line widths are much smaller than the Pearl length = 2λ 2 /d. We define the critical current as the current that reduces the Gibbs-free-energy barrier to zero. We show that current crowding, which occurs whenever the current rounds a sharp turn, tends to reduce the critical current, but we also show that when the radius of curvature is less than the coherence length, this effect is partially compensated by a radius-of-curvature effect. We propose several patterns with rounded corners to avoid critical-current reduction due to current crowding. These results are relevant to superconducting nanowire single-photon detectors, where they suggest a means of improving the bias conditions and reducing dark counts. These results also have relevance to normal-metal nanocircuits, as these patterns can reduce the electrical resistance, electromigration, and hot spots caused by nonuniform heating.

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Section: Discussionmentioning

confidence: 99%

Geometry-dependent critical currents in superconducting nanocircuits

2011

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“…For each sample geometry considered, they carried out a calculation of the Gibbs free energy similar to that in Eq. (2) and showed that when ξ W , the critical sheet-current density can be expressed as K c (0) = K cs R, where K cs is the critical sheet current for a long straight strip in the absence of an applied field [Eq. (5)] and R is a critical-current reduction • turn, shown by the contour plot of its stream function SIz(x, y).…”

Section: Ic(hz) For Strips With Left Turnsmentioning

confidence: 99%

“…On the practical side, numerous applications of superconductivity require the operating current to be as high as possible without exceeding the critical current. In this paper we focus on thin and narrow strips, where it is known that the critical current is dominated by the edge-pinning critical current, [1][2][3] which is generally much larger than the bulk-pinning critical current and can even approach the Ginzburg-Landau depairing critical current. 4 Pinning in thin films by the edge barrier is closely related to pinning in bulk superconductors by the Bean-Livingston barrier, 5,6 a barrier against vortex entry that permits high currents to be carried by the surface in parallel applied magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

Predicted field-dependent increase of critical currents in asymmetric superconducting nanocircuits

et al. 2012

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The critical current of a thin superconducting strip of width W much larger than the GinzburgLandau coherence length ξ but much smaller than the Pearl length Λ = 2λ 2 /d is maximized when the strip is straight with defect-free edges. When a perpendicular magnetic field is applied to a long straight strip, the critical current initially decreases linearly with H but then decreases more slowly with H when vortices or antivortices are forced into the strip. However, in a superconducting strip containing sharp 90-degree or 180-degree turns, the zero-field critical current at H = 0 is reduced because vortices or antivortices are preferentially nucleated at the inner corners of the turns, where current crowding occurs. Using both analytic London-model calculations and timedependent Ginzburg-Landau simulations, we predict that in such asymmetric strips the resulting critical current can be increased by applying a perpendicular magnetic field that induces a currentdensity contribution opposing the applied current density at the inner corners. This effect should apply to all turns that bend in the same direction.

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“…In contrast to previous works, which analyze the experimental data by treating the bridges as infinitesimal long bridges [12,13] (see Fig. 1(a)), here we take into account the influence of the wide electrodes, connecting the nano-bridge to the biasing circuit, on the critical current density (see Fig.…”

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confidence: 99%

Microwave Response of SuperconductingYBa2Cu3O7−δNanowire Bridges Sustaining the Critical Depairing Current: Evidence of Josephson-li

et al. 2013

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We have investigated the zero-field critical supercurrent of YBa 2 Cu 3 O 7−δ bridges patterned from 50 nm thick films as a function of bridge width, ranging from 2 µm to 50 nm. The critical current density monotonically increases for decreasing bridge width even for widths smaller than the Pearl length. This behavior is accounted for by considering current crowding effects at the junction between the bridge and the wider electrodes. Comparison to numerical calculations of the current distributions in our bridge geometries of various widths yields a (local) critical current density at 4.2 K of 1.3 × 10 8 A/cm 2 , the Ginzburg Landau depairing current density. The observation of up to 160 Shapiro-like steps in the current voltage characteristics under microwave irradiation substantiates the pristine character of our nano bridges with cross sections as small as 50 × 50 nm 2 .

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Impact of edge-barrier pinning in superconducting thin films

Cited by 18 publications

References 25 publications

Geometry-dependent critical currents in superconducting nanocircuits

Geometry-dependent critical currents in superconducting nanocircuits

Predicted field-dependent increase of critical currents in asymmetric superconducting nanocircuits

Microwave Response of SuperconductingYBa2Cu3O7−δNanowire Bridges Sustaining the Critical Depairing Current: Evidence of Josephson-li

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