Thermal hysteresis of the Campbell response as a probe for bulk pinning landscape spectroscopy

Willa, Roland; Bermúdez, Mariano Marziali; Pasquini, G.

doi:10.1103/physrevb.98.184520

Cited by 8 publications

(11 citation statements)

References 45 publications

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“…At the same time, an alternative viewpoint describing pinning due to a low density of strong centres was proposed early on, see Refs. [4] and [5]; recently, this strong pinning scenario has attracted increasing attention, particularly in studies of charge density waves [19, 21, and 22] and of magnetic flux-line lattices [23][24][25][26][27]. Although some effort has been made to qualitatively understand the crossover between the two regimes [28 and 29], a quantitative model describing this transition has not been developed so far.…”

Section: Introductionmentioning

confidence: 99%

The role of rare events in the pinning problem

Buchacek,

Geshkenbein,

Blatter

2020

Preprint

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Type II superconductors exhibit a fascinating phenomenology that is determined by the dynamical properties of the vortex matter hosted by the material. A crucial element in this phenomenology is vortex pinning by material defects, e.g., immobilizing vortices at small drives and thereby guaranteeing dissipation-free current flow. Pinning models for vortices and other topological defects, such as domain walls in magnets or dislocations in crystals, come in two standard variants: i) weak collective pinning, where individual weak defects are unable to pin, while the random accumulation of many force centers within a collective pinning volume combines into an effective pin, and ii) strong pinning, where strong defects produce large vortex displacements and bistabilities that lead to pinning on the level of individual defects. The transition between strong and weak pinning is quantified by the Labusch criterion κ ≈ fp/ Cξ = 1, where fp and C are the force of one defect and the effective elasticity of the vortex lattice, respectively (ξ is the coherence length). Here, we show that a third generic type of pinning becomes dominant when the pinning force fp enters the weak regime, the pinning by rare events. We find that within an intermediate regime 1/2 < κ < 1, compact pairs of weak defects define strong pinning clusters that extend the mechanism of strong pinning into the weak regime. We present a detailed analysis of this cluster-pinning mechanism and show that its pinning-force density parametrically dominates over the weak pinning result. The present work is a first attempt to include correlations between defects into the discussion of strong pinning.

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Section: Introductionmentioning

confidence: 99%

The role of rare events in the pinning problem

Buchacek,

Geshkenbein,

Blatter

2020

Preprint

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“…The limit of dilute, strong defects has been studied analytically in recent years. Contrary to the qualitative scaling arguments of weak collective pinning theory, the strong pinning framework provides quantitative results for various observables (J c 32,50,52,61,62 , Campbell penetration [63][64][65][66] , zero-and finite-temperature current-voltage characteristics. 34,35,67,68 ) Specifically, the critical current has been shown 52 to follow J c = J dp (n p a 0 ξ 2 )( f p /ε 0 ) 2 , over a wide field range, with J dp being the depairing current, n p the defect density, f p the elementary force provided by a single defect, and ε 0 the vortex line energy.…”

Section: Theoretical Backgroundmentioning

confidence: 84%

Designing high-performance superconductors with nanoparticle inclusions: comparisons to strong pinning theory

Jones,

Miura,

Yoshida

et al. 2021

Preprint

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One of the most promising routes for achieving unprecedentedly high critical currents in superconductors is to incorporate dispersed, non-superconducting nanoparticles to control the dissipative motion of vortices. However, these inclusions reduce the overall superconducting volume and can strain the interlaying superconducting matrix, which can detrimentally reduce T c . Consequently, an optimal balance must be achieved between the nanoparticle density n p and size d. Determining this balance requires garnering a better understanding of vortex-nanoparticle interactions, described by strong pinning theory. Here, we map the dependence of the critical current on nanoparticle size and density in (Y 0.77 ,Gd 0.23 )Ba 2 Cu 3 O 7−δ films in magnetic fields up to 35 T, and compare the trends to recent results from timedependent Ginzburg-Landau simulations. We identify consistencies between the field-dependent critical current J c (B) and expectations from strong pinning theory. Specifically, we find that that J c ∝ B −α , where α decreases from 0.66 to 0.2 with increasing density of nanoparticles and increases roughly linearly with nanoparticle size d/ξ (normalized to the coherence length). At high fields, the critical current decays faster (∼ B −1 ), suggestive that each nanoparticle has captured a vortex. When nanoparticles capture more than one vortex, a small, high-field peak is expected in J c (B). Due to a spread in defect sizes, this novel peak effect remains unresolved here. Lastly, we reveal that the dependence of the vortex creep rate S on nanoparticle size and density roughly mirrors that of α, and compare our results to low-T nonlinearities in S(T ) that are predicted by strong pinning theory.

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“…While conceptually simpler than weak collective pinning, it has taken significantly longer to develop a strong pinning formalism. With its completion in the early 2000s, the formalism enabled computing numerous physical observables, including the critical current 53,54 , the excess-current characteristic [55][56][57][58][59][60] , and the ac Campbell response [11][12][13][14] .…”

Section: A Fundamentals Of Vortex Pinningmentioning

confidence: 99%

“…Additionally, it has determined the optimal shape, size, and dimensionality of defects necessary to maximize J c , depending on the magnitude and orientation of the magnetic field [7][8][9][10] . Backed by good agreement with experimental and analytic results for simple geometries [11][12][13][14] , the utility of the numerical routine has successfully been extended to previously unknown territories, optimizing pinning geometries outside the scope of analytic methods [2][3][4][7][8][9][10][15][16][17][18] . In fact, these TDGL simulations have unveiled new phenomena-such as a small peak in J c (B) at high fields that is caused by double vortex occupancy of individual pinning sites.…”

Section: Introductionmentioning

confidence: 99%

Perspective: Challenges and Transformative Opportunities in Superconductor Vortex Physics

Eley,

Glatz,

Willa

2021

Preprint

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In superconductors, the motion of vortices introduces unwanted dissipation that is disruptive to applications. Fortunately, material defects can immobilize vortices, acting as vortex pinning centers, which engenders dramatic improvements in superconductor material properties and device operation. This has motivated decades of research into developing methods of tailoring the disorder landscape in superconductors to increase the strength of vortex pinning. Yet efficacious materials engineering still alludes us. The electromagnetic properties of real (disordered) superconducting materials cannot yet be reliably predicted, such that designing superconductors for applications remains a largely inefficient process of trial and error. This is ultimately due to large gaps in our knowledge of vortex dynamics: the field is challenged by the extremely complex interplay between vortex elasticity, vortex-vortex interactions, and material disorder.In this Perspective, we review obstacles and recent successes in understanding and controlling vortex dynamics in superconducting materials and devices. We further identify major open questions and discuss opportunities for transformative research in the field. This includes improving our understanding of vortex creep, determining and reaching the ceiling for the critical current, advanced microscopy to garner accurate structure-property relationships, frontiers in predictive simulations and the benefits of artificial intelligence, as well as controlling and exploiting vortices in quantum information applications.

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Thermal hysteresis of the Campbell response as a probe for bulk pinning landscape spectroscopy

Cited by 8 publications

References 45 publications

The role of rare events in the pinning problem

The role of rare events in the pinning problem

Designing high-performance superconductors with nanoparticle inclusions: comparisons to strong pinning theory

Perspective: Challenges and Transformative Opportunities in Superconductor Vortex Physics

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