University of Illinois Urbana-Champaign

Imaging vortices in superconducting weakly coupled arrays

Wistrom, Mark

Content Files
Wistrom_Mark.pdf

Permalink

https://hdl.handle.net/2142/31039

Description

Title
Imaging vortices in superconducting weakly coupled arrays
Author(s)
Wistrom, Mark
Issue Date
2012-05-22T00:23:44Z
Director of Research (if dissertation) or Advisor (if thesis)
Van Harlingen, Dale J.
Doctoral Committee Chair(s)
Mason, Nadya
Committee Member(s)
  • Van Harlingen, Dale J.
  • Ryu, Shinsei
  • Clegg, Robert M.
Department of Study
Physics
Discipline
Physics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Date of Ingest
2012-05-22T00:23:44Z
Keyword(s)
  • Scanning SQUID Microscope
  • Superconducting arrays
Abstract
This thesis presents the direct observations of magnetic flux vortices in superconducting weakly coupled arrays. Real space images of vortices were obtained for various values of f, the fractional flux per unit cell in the array, and , the strength of the coupling between the islands of the superconducting array. Images and results were obtained for a single vortex in a triangular array, demonstrating the effect of changing , which increased the penetration depth of the magnetic field of the vortex in the sample. The ground state of a triangular array is measured and discussed as a function of f with emphasis for f = 1/4, 1/3 where there are several degenerate ground states corresponding to different vortex patterns. Annealing the arrays at a particular f is also discussed. In particular, for a square array at f = 1/2, the domain walls are the dominant defects, and they move through the sample as the temperature increases resulting in a single domain. The instrument used to perform the experiments, a Scanning SQUID Microscope (SSM), is discussed. The vortices in the superconducting arrays have weak magnetic fields that change over small length scales, requiring certain techniques for measurement. Also presented are the numerical calculations relating the magnetic field output from the SSM to the underlying phases of the array.
Graduation Semester
2012-05
Permalink
http://hdl.handle.net/2142/31039
Copyright and License Information
Copyright 2012 Mark Wistrom

Owning Collections

Graduate Dissertations and Theses at Illinois PRIMARY
Graduate Theses and Dissertations at Illinois
Dissertations and Theses - Physics
Dissertations in Physics