Superconducting transition and vortex pinning in Nb films patterned with nanoscale hole arrays

Welp, U.; Xiao, Z. L.; Jiang, J. S.; Vlasko-Vlasov, Vitalii; Bader, S. D.; Crabtree, G. W.; Liang, Jianyu; Chik, H.; Xu, Jimmy

doi:10.1103/physrevb.66.212507

Cited by 99 publications

(92 citation statements)

References 54 publications

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“…During the past decade, compelling evidence has shown that the introduction of an array of microholes ͑antidots͒ in a superconducting film has a profound influence on both the critical current 1,2 I c ͑H͒ and the critical temperature 3,4 T c ͑H͒. Typically, at temperatures used for transport measurements, the antidots are able to trap only one flux quantum ⌽ 0 before saturation sets in.…”

Section: Introductionmentioning

confidence: 99%

Enhanced vortex pinning by a composite antidot lattice in a superconducting Pb film

et al. 2005

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The use of artificial defects is known to enhance the superconducting critical parameters of thin films. In the case of conventional superconductors, regular arrays of submicron holes ͑antidots͒ substantially increase the critical temperature T c ͑H͒ and critical current I c ͑H͒ for all fields. Using electrical transport measurements, we study the effect of placing an additional small antidot in the unit cell of the array. This composite antidot lattice consists of two interpenetrating antidot square arrays with a different antidot size and the same lattice period. The smaller antidots are located at the centers of the cells of the large antidots array. We show that the composite antidot lattice can trap a higher number of flux quanta per unit cell inside the antidots compared to a reference antidot film without the additional small antidots. As a consequence, the field range in which an enhanced critical current is observed is considerably expanded. Finally, the possible stable vortex lattice patterns at several matching fields are determined by molecular-dynamics simulations.

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Section: Introductionmentioning

confidence: 99%

Enhanced vortex pinning by a composite antidot lattice in a superconducting Pb film

et al. 2005

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“…The amplitude of the oscillations, however, depends strongly on the reduced resistances, R(T )/R N , at which they are measured. That is, unlike thicker films the shape of the transitions change in field [20,21]. Figure 2 shows a typical series of isodissipative (i.e.…”

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confidence: 99%

“…1) [18,19]. For example, the resistive transitions of thick Nb films [20] on nanopore arrays and thick Al films with much larger lattice and hole dimensions [21] oscillate in temperature while maintaining their shape in an applied magnetic field. For holes separated by segments on the order of ξ 0 or less [20] ∆T c T c0…”

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confidence: 99%

Magnetic-flux periodic response of nanoperforated ultrathin superconducting films

et al. 2006

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We have patterned a hexagonal array of nano-scale holes into a series of ultrathin, superconducting Bi/Sb films with transition temperatures 2.65 K < Tco <5 K. These regular perforations give the films a phase-sensitive periodic response to an applied magnetic field. By measuring this response in their resistive transitions, R(T ), we are able to distinguish regimes in which fluctuations of the amplitude, both the amplitude and phase, and the phase of the superconducting order parameter dominate the transport. The portion of R(T ) dominated by amplitude fluctuations is larger in lower Tco films and thus, grows with proximity to the superconductor to insulator transition.The superconductors originally considered by BCS exhibited spectacularly sharp transitions from a finite resistance to zero resistance as a function of temperature [1]. Fluctuation effects were negligible. Presently, a great deal of attention focuses on low superfluid density superconductors for which fluctuations strongly influence and substantially broaden their phase transitions. These include the high temperature superconductors [2], and in particular, their underdoped versions [3,4,5], and ultrathin superconducting films near the superconductor to insulator transition (SIT) [6,7,8,9,10]. For the latter, resistive transitions, R(T ), can develop widths comparable to or greater than the apparent mean field transition temperature, T c0 [11].To discuss the effects of fluctuations on the R(T ) it is helpful to consider the two component superconductor order parameter ψ = |ψ 0 |e iφ . In bulk elemental superconductors, the sharp R(T ) reflect the near simultaneous appearance of a finite amplitude, |ψ 0 |, and long range coherence of the phase, φ. In low superfluid density superconductors, however, the amplitude first forms at high temperatures and phase coherence develops at lower temperatures [2,12,13,14]. High on a transition quasiparticles transiently form Cooper pairs, which enhances the quasiparticle or fermionic contribution to the conductivity, σ f . These pair or amplitude fluctuations give rise to the initial drop in R(T ) [15]. At very low values of R, a substantial Cooper pair density exists and the conductivity of these bosons, σ b , controls R(T ). σ b is limited by the motion of vortices which causes fluctuations in the phase of the cooper pair condensate. In between, a two fluid model may best describe the transport [7].Physical interpretations of the R(T ) in high sheet resistance films especially those near the SIT relies heavily on distinguishing the amplitude and phase fluctuation dominated regimes [3,4,5,6]. Most often, explicit models for σ f (T ) and σ b (T ) do not exist as a guide and qualitative arguments must prevail. In this paper we present the magnetic flux response of the R(T ) of very low superfluid density (high sheet resistance) [11,16] films patterned with a nanoscale array of holes. We use the quality of the flux response at different points along their transitions to determine the presence of well-defined vortic...

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“…We focus our analysis on the data obtained within the range of temperatures 7.5K < T < 7.52K < T c , where T c ≃ 7.55K is the superconducting critical temperature of the sample, and the range of current densities 10A/cm 2 < J < 27A/cm 2 . For lower temperatures or currents the commensurability effects are weak, presumably due to the dominance of the intrinsic pinning mechanisms over the periodic potential [39,40,41]. For temperatures or currents above the selected intervals, we observed a finite dissipation at zero external magnetic field which indicates the presence of vortices induced by the external current or other dissipation mechanisms.…”

Section: Magnetoresistance Measurementsmentioning

confidence: 79%

Vortex kinks in superconducting films with periodically modulated thickness

Facio¹,

Abate²,

Guimpel³

et al. 2013

J. Phys.: Condens. Matter

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We report magnetoresistance measurements in Nb films having a periodic thickness modulation. The cylinder shaped thicker regions of the sample, which form a square lattice, act as repulsive centers for the superconducting vortices. For low driving currents along one of the axes of the square lattice, the resistivity ρ increases monotonously with increasing magnetic field B and the ρ–B characteristics are approximately piecewise linear. The linear ρ versus B segments change their slope at matching fields where the number of vortices is an integer or a half integer times the number of protruding cylinders in the sample. Numerical simulations allow us to associate the different segments of linear magnetoresistance to different vortex-flow regimes, some of which are dominated by the propagation of discommensurations (kinks).

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Superconducting transition and vortex pinning in Nb films patterned with nanoscale hole arrays

Cited by 99 publications

References 54 publications

Enhanced vortex pinning by a composite antidot lattice in a superconducting Pb film

Enhanced vortex pinning by a composite antidot lattice in a superconducting Pb film

Magnetic-flux periodic response of nanoperforated ultrathin superconducting films

Vortex kinks in superconducting films with periodically modulated thickness

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