Abstract/Details

A numerical study of steady-state vortex configurations and vortex pinning in type -II superconductors


2004 2004

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Abstract (summary)

In part I, a numerical study of the mixed states in a mesoscopic type-II superconducting cylinder is described. Steady-state configurations and transient behavior of the magnetic vortices for various values of the applied magnetic field H are presented. Transitions between different multi-vortex states as H is changed is demonstrated by abrupt changes in vortex configurations and jumps in the B vs. H plot. An efficient scheme to determine the equilibrium vortex configuration in a mesoscopic system at any given applied field, not limited to the symmetry of the system, is devised and demonstrated.

In part II, a superconducting thin film is subject to a non-uniform magnetic field from a vertical magnetic dipole, consisting of two magnetic monopoles of opposite charges. For a film with constant thickness and with no pins, it has been found that the film carries two pairs of vortex-antivortex in the steady state in the imposed flux range of 2.15 < Φ+</super> < 2.90 (in units of flux quantum) and no vortex at all for Φ + ≤ 2.15. Transitions from a superconducting state with 3 pairs of vortex-antivortex to one with 2 pairs, where a pair of vortex-antivortex annihilates, have been observed in the pseudo-time sequence. With a perturbation with antidots (holes), vortex-antivortex pair has been created for lower magnetic fluxes down to Φ+ = 1.3.

In the sample of size 16ξ × 16ξ, the attraction force between the vortex and antivortex always dominates over the pinning force, so that they eventually come out of pins, move toward each other, and annihilate each other. The annihilation rate, measured with time taken for the annihilation, is reduced noticeably by the increase of the distance between pins, or the increase in the pin size. A simulation of the magnetic vortex pinning in the sample of size 32ξ × 32ξ suggests we are likely to achieve pinning of the vortex-antivortex pair with the sample size around this and vortex-antivortex separation of 22ξ. Using this sample as a template, the maximum density of pinned vortices achievable is calculated to be about 7.6 × 10 14 vortices/m2 for ξ ≅ 1.6 Å.

Indexing (details)


Subject
Condensation;
Materials science
Classification
0611: Condensation
0794: Materials science
Identifier / keyword
Applied sciences; Pure sciences; Steady-state; Superconductors; Type-II superconductors; Vortex pinning
Title
A numerical study of steady-state vortex configurations and vortex pinning in type -II superconductors
Author
Kim, Sangbum
Number of pages
164
Publication year
2004
Degree date
2004
School code
0803
Source
DAI-B 66/12, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
0542472961, 9780542472961
Advisor
Andrews, Malcolm J.; Hu, Chia-Ren
University/institution
Texas A&M University
University location
United States -- Texas
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3202249
ProQuest document ID
305070015
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305070015
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