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Title: 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.

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [3];  [4]
  1. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division; Northwestern Univ., Evanston, IL (United States). Dept. of Engineering Sciences and Applied Mathematics
  2. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division; Northern Illinois Univ., DeKalb, IL (United States). Dept. of Physics
  3. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division
  4. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division; Univ. of Chicago, IL (United States). Computation Inst.
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21). Scientific Discovery through Advanced Computing (SciDAC)
OSTI Identifier:
1493704
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 9; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Type-II superconductivity; critical current; vortex trapping; Bean-Livingston barrier; time-dependent Ginzburg-Landau model

Citation Formats

Kimmel, Gregory J., Glatz, Andreas, Vinokur, Valerii M., and Sadovskyy, Ivan A. Edge effect pinning in mesoscopic superconducting strips with non-uniform distribution of defects. United States: N. p., 2019. Web. doi:10.1038/s41598-018-36285-4.
Kimmel, Gregory J., Glatz, Andreas, Vinokur, Valerii M., & Sadovskyy, Ivan A. Edge effect pinning in mesoscopic superconducting strips with non-uniform distribution of defects. United States. doi:10.1038/s41598-018-36285-4.
Kimmel, Gregory J., Glatz, Andreas, Vinokur, Valerii M., and Sadovskyy, Ivan A. Fri . "Edge effect pinning in mesoscopic superconducting strips with non-uniform distribution of defects". United States. doi:10.1038/s41598-018-36285-4. https://www.osti.gov/servlets/purl/1493704.
@article{osti_1493704,
title = {Edge effect pinning in mesoscopic superconducting strips with non-uniform distribution of defects},
author = {Kimmel, Gregory J. and Glatz, Andreas and Vinokur, Valerii M. and Sadovskyy, Ivan A.},
abstractNote = {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.},
doi = {10.1038/s41598-018-36285-4},
journal = {Scientific Reports},
issn = {2045-2322},
number = 1,
volume = 9,
place = {United States},
year = {2019},
month = {1}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Figures / Tables:

Figure 1 Figure 1: (a) Two-dimensional superconducting strip of width W = 64ξ with non-homogeneous inclusion distribution. The current J is applied vertically (along the x-axis), the magnetic field B is perpendicular to the figure plane, and the resulting Lorentz force FL acts to the right (along the y-axis). The sample hasmore » a length of L = 1024ξ with quasi-periodic boundary conditions in the x direction; in the y direction, we have open boundary conditions, i.e., superconductor-vacuum surfaces. The strip contains (uncorrelated) randomly placed circular inclusions of diameter d = 3ξ. The density of these inclusions depends on y: in the middle of the sample, the volume fraction occupied by inclusions is f = 0.2, which corresponds approximately to conditions for the maximum possible critical current density in bulk samples. The density of the inclusion ρi(y) decreases linearly near the sample boundaries (see bottom plot): within a region of width lin at the boundary where vortices enter the sample and lout at the boundary where vortices leave the sample. (b) The critical current Jc as a function of lin and lout normalized by Jc(0, 0) at applied magnetic field B = 0.1Hc2. The critical current is increased by ~30% for finite lin and lout compared to the critical current from a homogeneous defect distribution (lin = lout = 0). The values of lin and lout corresponding to the maximum of the critical current Jc(lin, lout) are shown by colored circles for B = 0.1Hc2, 0.2Hc2, and 0.3Hc2. The effect is asymmetric and depends on the direction of vortex motion. The maximum is indicated by a (blue) circle. Corresponding maxima for fields 0.2Hc2 and 0.3Hc2 are indicated by (cyan and green) circles, marked by the field value.« less

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