Edge effect pinning in mesoscopic superconducting strips with non-uniform distribution of defects

Abstract

Transport characteristics of nano-sized superconducting strips and bridges are determined by an intricate interplay of surface and bulk pinning. In the limiting case of a very narrow bridge, the critical current is mostly defined by its surface barrier, while in the opposite case of very wide strips it is dominated by its bulk pinning properties. Here we present a detailed study of the intermediate regime, where the critical current is determined, both, by randomly placed pinning centres and by the Bean-Livingston barrier at the edge of the superconducting strip in an external magnetic field. We use the time-dependent Ginzburg-Landau equations to describe the vortex dynamics and current distribution in the critical regime. Our studies reveal that while the bulk defects arrest vortex motion away from the edges, defects in their close vicinity promote vortex penetration, thus suppressing the critical current. We determine the spatial distribution of the defects optimizing the critical current and find that it is in general non-uniform and asymmetric: the barrier at the vortex-exit edge influence the critical current much stronger than the vortex-entrance edge. Furthermore, this optimized defect distribution has a more than 30% higher critical current density than a homogeneously disorder superconducting film.

Perspective: Challenges and Transformative Opportunities in Superconductor Vortex Physics

“…3a). Prior to this study, we had speculated that creep for other Fe-SCs seemed surprisingly fast [5][6][7][8][9][10] , which raised an important question: precisely what should we expect and how much lower can we go?…”

“…Significant headway has been made along these lines with the implementation of large-scale time-dependent Ginzburg-Landau (TDGL) simulations to study vortex motion through disordered media. Spearheaded by the Argonne National Laboratory, this effort has accurately modeled critical currents J c in thin films (2D), layered and anisotropic 3D materials, as well as isotropic superconductors [2][3][4][5][6] . 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] .…”

Thermo-Magnetic Signature of a Superconducting Multi-band Square with Rough Surface

“…The effect of a triangular arrangement of punctual defects on vortex configuration in a thin circular mesoscopic sample was done [10], they found non-commensurate vortex configurations due to the interplay between the vortex-vortex repulsion, the vortex-defect interaction and the interaction with the sample border. Numerical simulation of transport characteristic of a mesoscopic superconducting strip with randomly placed pinning centers and taking into account the Bean-Livingston barrier at the edges in an external magnetic field was realized [11]. Experimental and theoretical studies show that at small magnetic fields, there is a discontinuity in heat capacity at critical temperature ( T c ) as the bulk superconductors.…”

Supercurrent Induced by Chiral Coupling in Multiferroic/Superconductor Nanostructures

“…They are not only a source of irreversibility of the superconductor’s magnetic response, but they can also serve to keep fluxons out of the SC, improving the device efficiency. In combination with conventional pinning methods, the exploitation of the penetration barrier can greatly enhance the critical current of an SC [ 11 ]. The problem of the surface barrier has been under investigation for several decades and is still of current importance.…”