Probing the low-frequency vortex dynamics in a nanostructured superconducting strip

Silva, Clécio C. de Souza; Raes, Bart; Brisbois, Jérémy; Cabral, Leonardo R.E.; Silhanek, Alejandro; Vondel, J. Van de; Moshchalkov, Victor

doi:10.1103/physrevb.94.024516

Cited by 4 publications

(3 citation statements)

References 45 publications

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“…Low k-vectors, or wave-lengths comparable to the sample size, leads to highly dispersive elastic moduli which modify the attempt frequency by orders of magnitude [60][61][62] . Similar to our observation, previous measurements of slow vortex dynamics have reported 63,64 very low frequency values for thermal motion and creep. Creep rates observed in layered cuprate superconductors involve extremely large time scales, indicating the relevance of col-lective creep 2,3,60,62 .…”

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confidence: 93%

Thermal creep induced by cooling a superconducting vortex lattice

Willa

Galvis

Benito-Llorens

et al. 2020

Phys. Rev. Research

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A perturbed system relaxes towards an equilibrium given by a minimum in the potential energy landscape. This often occurs by thermally activated jumps over metastable states. The corresponding dynamics is named creep and follows Arrhenius' law. Here we consider the situation where the equilibrium position depends on temperature. We show that this effect occurs in the vortex lattice of the anisotropic superconductor 2H-NbSe2 when the magnetic field is tilted away from the principal axes, and that it leads to the peculiar appearance of creep when cooling the sample. Temperature determines the system's ground state and at the same time brings the system back to equilibrium, playing a dual and antagonistic role. We expect that cooling induced creep occurs in correlated systems with many degrees of freedom allowing to tune the equilibrium state via heat treatment.Superconducting vortices are lines of quantized magnetic flux Φ 0 = hc/2e where the superconducting order parameter is depressed at a length scale of order of the superconducting coherence length ξ and circular supercurrents are flowing at a length scale of order of the penetration depth λ. Vortices arrange in a lattice, which can be triangular, square or disordered due to the interactions of vortices with the crystalline environment 1-5 . Vortices tend to be pinned on material defects or inclusions consisting of places where superconductivity is depressed on length scales of order ξ. When varying the applied magnetic field, its strength or direction, vortices enter or exit the sample 1-3 . This produces vortex motion, which is often counteracted by pinning. The action of the pinning landscape results in long-lived out-of-equilibrium vortex distributions that relax through thermal creep over a manifold of barriers 1-3,6-10 . The phenomenon of creep has been observed in interacting systems of particles, such as colloids, polymers, solids consisting of mixtures or in lattices of entities formed through electronic interactions (domain walls or skyrmions) [11][12][13][14][15] . Vortex lattices are often considered as a model system. Most efforts to understand vortex creep have focused on trying to immobilize vortices and thereby increase the critical current j c for applications 16 . But the interaction between vortices and the underlying superconducting material is very rich and can produce counterintuitive phenomena. Here we find that the equilibrium state towards which the system creeps can be modified with the temperature, leading to a phenomenon that we term self-imposed creep. We study vortex creep in the the superconductor 2H-NbSe 2 and we observe that, as a consequence of self-imposed creep, the vortex lattice starts creeping when cooling, see Fig. 1. The layered system 2H-NbSe 2 shows weak pinning and small creep rates. Vortex properties depend crucially on random disorder potential cooling creep fast relaxation warming ξ U 0 x V(x) self-imposed FIG. 1. Schematic response of a particle confined in a potential subject to random disorder. The disorder pote...

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supporting

confidence: 93%

Thermal creep induced by cooling a superconducting vortex lattice

Willa

Galvis

Benito-Llorens

et al. 2020

Phys. Rev. Research

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“…For the particular case of superconducting strips, some works had been conducted investigating vortex states, critical currents, and magnetization curves [76][77][78][79][82][83][84][85][86][87][88][89][90]. In strips, vortices arrange themselves in chains of straight vortex lines due to the geometrical constraint [76], and the magnetization curves present several peaks, indicating the vortex lattice transitions with formation or destruction of the vortex chains [78,88].…”

Section: Introductionmentioning

confidence: 99%

“…In strips, vortices arrange themselves in chains of straight vortex lines due to the geometrical constraint [76], and the magnetization curves present several peaks, indicating the vortex lattice transitions with formation or destruction of the vortex chains [78,88]. However, there are only few works investigating vortex dynamics under the influence of pinning centers in strips [72,77,86].…”

Section: Introductionmentioning

confidence: 99%

Surface Effects on the Dynamic Behavior of Vortices in Type II Superconducting Strips with Periodic and Conformal Pinning Arrays

Vizarim

Carlone

Verga

et al. 2017

J Supercond Nov Magn

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Using molecular dynamics techniques, we simulate the vortex behavior in a type II superconducting strip in the presence of triangular and two types of conformal pinning arrays, one with a pinning gradient perpendicular to the driving force (C1) and the other parallel (C2), at zero temperature. A transport force is applied in the infinite direction of the strip, and the magnetic field is increased until the rate between the density of vortices (n v ) and pinning (n p ) reaches n v /n p = 1.5. Our results show a monotonic increase, by steps, of the vortex density with the applied magnetic field. Besides, each pinning lattice presents a different vortex penetration delay. For the triangular pinning array, different than the case of infinite films, here the system exhibits only one pronounced depinning force peak at n v /n p = 1. However, the depinning force peak is present for only one value of field, in the range of fields where n v /n p = 1 is stable. For the case of conformal pinning arrays, in analogy to what is observed in infinite films, no commensurability depinning force peaks were found. In the present case, the C1 array is more efficient at low fields, all arrays are equivalent in the intermediate fields, and the C2 array is more efficient for high fields. We also show that for the C1 array at high fields, vortices depin following the conformal arches, from the edge to the center. For the C2 array, the depinning force is higher when compared to that of C1, because this particular conformal structure prevents the formation of easy vortex flow channels.

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