Strong-pinning regimes by spherical inclusions in anisotropic type-II superconductors

Abstract

The current-carrying capacity of type-II superconductors is decisively determined by how well material defect structures can immobilize vortex lines. In order to gain deeper insights into the fundamental pinning mechanisms, we have explored the case of vortex trapping by randomly distributed spherical inclusions using large-scale simulations of the time-dependent Ginzburg-Landau equations. We find that for a small density of particles having diameters of two coherence lengths, the vortex lattice preserves its structure and the critical current $j_c$ decays with the magnetic field following a power-law $B^{-\alpha }$ with $\alpha \approx 0.66$, which is consistent with predictions of strong-pinning theory. For a higher density of particles and/or larger inclusions, the lattice becomes progressively more disordered and the exponent smoothly decreases down to $\alpha \approx 0.3$. At high magnetic fields, all inclusions capture a vortex and the critical current decays faster than $B^{-1}$ as would be expected by theory. In the case of larger inclusions with a diameter of four coherence length, the magnetic-field dependence of the critical current is strongly affected by the ability of inclusions to capture multiple vortex lines. We found that at small densities, the fraction of inclusions trapping two vortex lines rapidly grows within narrow field range leading to a peak in $j_c(B)$-dependence within this range. With increasing inclusion density, this peak transforms into a plateau, which then smooths out. Using the insights gained from simulations, we determine the limits of applicability of strong-pinning theory and provide different routes to describe vortex pinning beyond those bounds.

24 pages, 16 figures

References in corpus (5)

• Stable large-scale solver for Ginzburg-Landau equations for superconductors
• Depinning and creep motion in glass states of flux lines
• Artificial and self-assembled pinning centers in Ba(Fe1-xCox)2As2 thin films as a route to very high current density
• Effect of hexagonal patterned arrays and defect geometry on the critical current of superconducting films
• In silico optimization of critical currents in superconductors

Cited by in corpus (13)

• Perspective: Challenges and Transformative Opportunities in Superconductor Vortex Physics
• The quest for high critical current in applied high-temperature superconductors
• Strong pinning theory of thermal vortex creep in type II superconductors
• Scanning quantum vortex microscopy reveals thickness-dependent pinning nano-network in superconducting Nb-films
• Effects of 6 MeV proton irradiation on the vortex ensemble in BaFe${}_2$(As${}_{0.67}$P${}_{0.33}$)${}_2$ revealed through magnetization measurements and real-space vortex imaging
• Noise signal as input data in self-organized neural networks
• Magnetic force microscopy versus scanning quantum-vortex microscopy: Probing pinning landscape in granular niobium films
• Magnetic flux trapping in porous superconductors
• Disorder-induced trapping and anti-trapping of vortices in type-II superconductors
• Increase of critical current density in FeSe superconductor by strain effect
• Vortex matter and strong pinning in underdoped PrFeAs(O,F) with atomic-sized defects
• Higher critical currents yet faster vortex creep in EuBa${}_2$Cu${}_3$O${}_y$ films containing coherent artificial pinning centers
• Designing high-performance superconductors with nanoparticle inclusions: comparisons to strong pinning theory