Vortex plastic flow, local flux density, magnetization hysteresis loops, and critical current, deep in the Bose-glass and Mott-insulator regimes

Reichhardt, C.; Olson, C. J.; Groth, J.; Field, Stuart B.; Nori, Franco

doi:10.1103/physrevb.53.r8898

Cited by 93 publications

(96 citation statements)

References 20 publications

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“…2b. These two vortex states have been well observed in high-κ systems with pure intervortex repulsion 23,[25][26][27][28][29][30][31] . We thus conclude that for strong pinning and moderate driving forces both for low-κ and high-κ vortex system the driven vortex states are dominated by pinning and that the details of the intervortex interactions are not so important.…”

mentioning

confidence: 66%

Vortex dynamics for low-κtype-II superconductors

Fangohr

Wang

et al. 2011

Phys. Rev. B

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mentioning

confidence: 66%

Vortex dynamics for low-κtype-II superconductors

Fangohr

Wang

et al. 2011

Phys. Rev. B

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“…2) at randomly chosen nonoverlapping positions until the desired maximum external field value is reached. As the vortex or antivortex density builds up in the pin-free region, the vortices or antivortices drive themselves into the pinned region due to their own repulsive interactions, creating a gradient in the flux density within the pinned region 14,31,32 . We then remove vortices from the pinfree region until the vortex density in this region reaches zero.…”

Section: The Dynamics Of Vortex I Are Obtained By Integrating the Ovementioning

confidence: 99%

“…We use periodic boundary conditions in the x and y-directions and consider a 36λ×36λ system with pinned region extending from x = 6λ to 30λ, where λ is the penetration depth. This geometry was previously shown to be large enough to capture accurately the behavior of the magnetization curves 14,31,32 . …”

mentioning

confidence: 99%

Strongly Enhanced Pinning of Magnetic Vortices in Type-II Superconductors by Conformal Crystal Arrays

Ray¹,

Jankó²,

Reichhardt³

2013

Phys. Rev. Lett.

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Conformal crystals are non-uniform structures created by a conformal transformation of regular two-dimensional lattices. We show that gradient-driven vortices interacting with a conformal pinning array exhibit substantially stronger pinning effects over a much larger range of field than found for random or periodic pinning arrangements. The pinning enhancement is partially due to matching of the critical flux gradient with the pinning gradient, but the preservation of the sixfold ordering in the conformally transformed hexagonal lattice plays a crucial role. Our results can be generalized to a wide class of gradient-driven interacting particle systems such as colloids on optical trap arrays.PACS numbers: 74.25. Wx,74.25.Uv One of the most important problems for applications of type-II superconductors is how to create high critical currents or strong vortex pinning over a wide range of applied magnetic fields 1 . For over sixty years, it has been understood that the ground state vortex structure is a hexagonal lattice 2 , so many methods have been developed to increase the critical current using uniform pinning arrays that incorporate periodicity to match the vortex structure 3-13 . The pinning is enhanced at commensurate fields when the number of vortices equals an integer multiple of the number of pinning sites, but away from these specific matching fields, the enhancement of the critical current is lost 14 . Efforts to enhance the pinning at incommensurate fields have included the use of quasicrystalline substrates 15 or diluted periodic arrays [16][17][18][19][20] , where studies show that new types of non-integer commensurate states can arise in addition to the integer matching configurations. Hyperbolic tessellation arrays were also recently considered 21 .Part of the problem is the fact that under an applied current, the vortex structure does not remain uniform but instead develops a Bean-like flux gradient 22 : the vortex density is highest at the edges of the sample when the magnetic field is increased, and highest in the center of the sample when the magnetic field is removed and only trapped flux remains inside the sample. As a consequence, uniform pinning arrays generally have a portion of the pinning sites that are not fully occupied, suggesting that a more optimal pinning arrangement should include some type of density gradient to match the critical flux gradient. Here we show that a novel type of pinning structure, created using a conformal transformation of a uniform hexagonal lattice, produces a much higher critical current over a much wider range of magnetic fields than any pinning geometry considered up until now. Conformal crystals not only have a density gradient, but also preserve aspects of the hexagonal ordering naturally adopted by the vortex lattice. The pinning enhancement we find is substantial and will be very important for a wide range of superconductor applications and flux control. Our results can also be important for stabilizing novel self-assembled structures created using de...

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“…They elucidated many properties of the Bean state including the magnetic field profile, magnetization hysteresis loops, critical currents, vortex avalanches, and vortex rivers [5][6][7][8][9][10]. None of these studies using an open system with an overall density gradient reported the IV characteristics, though.…”

Section: Some Comments On Conventional Theorymentioning

confidence: 99%

“…It has been recognized for many years that, in the presence of pinning, magnetic flux in type II superconductors forms a pile with an overall, global slope, akin to a sandpile. Penetration of magnetic flux into superconductors driven solely by the flux density gradient has been described using molecular dynamics (MD) simulations [5][6][7][8][9][10], and by the model used here [4]. However, the flux gradient has not been taken into account in any previous numerical simulation studies of the current-voltage characteristic.…”

Section: Introductionmentioning

confidence: 99%

Simple model for plastic dynamics of a disordered flux-line lattice

2001

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We use a coarse-grained model of superconducting vortices driven through a random pinning potential to study the nonlinear current-voltage (IV) characteristics of flux flow in type II superconductors with pinning. In experiments, the IV relation measures flux flow down a flux density gradient. The work presented here treats this key feature explicitly. As the vortex repulsion weakens, the vortex pile maintains a globally steeper slope, corresponding to a larger critical current, for the same pinning potential. In addition, the magnitude of the peak in the differential resistance falls as the resistance peak shifts to higher currents. The model also exhibits so-called "IV fingerprints", and crossover to Ohmic (linear) behavior at high currents. Thus, many of the varieties of plastic behavior observed experimentally for soft flux line systems in the "peak regime" are reproduced in numerical simulations of the zero temperature model. This model describes a two-dimensional slice of the flux line system at the scale of the London length (λ). It does not include any degrees of freedom at scales much smaller than λ, which are required to specify the degree of disorder in a flux line lattice. Instead, the nonlinear transport behaviors are related to the self-organized, large scale morphologies of the vortex river flow down the slope of the vortex pile. These morphologies include isolated filamentary channels, which can merge at higher flow rates to make a braided river, and eventually give uniform flow at even higher flow rates. The filamentary structure is associated with an IV characteristic that has concave, or positive, curvature. The braided river is associated with the peak in the differential resistance, where the curvature of the IV relation changes to convex. The transition to Ohmic behavior comes about as the braided river floods when it cannot absorb a higher level of flow. We propose that these self-organized morphologies of flux flow down a flux gradient govern the various plastic flow behaviors, including nonlinear IV characteristics, observed in type II superconductors with random pinning.

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Vortex plastic flow, local flux density, magnetization hysteresis loops, and critical current, deep in the Bose-glass and Mott-insulator regimes

Cited by 93 publications

References 20 publications

Vortex dynamics for low-κtype-II superconductors

Vortex dynamics for low-κtype-II superconductors

Strongly Enhanced Pinning of Magnetic Vortices in Type-II Superconductors by Conformal Crystal Arrays

Simple model for plastic dynamics of a disordered flux-line lattice

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