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Critical field for complete vortex expulsion from narrow superconducting strips.
Gheorghe Stan1, Stuart B Field, John M Martinis
1Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA.
Physical Review Letters
|April 20, 2004
Summary
Researchers measured the maximum magnetic field for vortex expulsion in thin-film superconducting strips. Narrower niobium wires expelled magnetic flux more effectively, suggesting device design considerations for noise reduction.
Area of Science:
- Condensed Matter Physics
- Materials Science
Background:
- Superconductors exhibit quantum phenomena like flux expulsion.
- Vortex behavior in thin films is crucial for superconducting device applications.
Purpose of the Study:
- To determine the maximum magnetic field for complete vortex expulsion from thin-film superconducting strips.
- To investigate the relationship between strip width and critical magnetic field for flux expulsion.
Main Methods:
- Field cooling niobium strips of varying widths.
- Imaging flux expulsion using a scanning Hall-probe microscope.
Main Results:
- Identified a critical field B(m) approximately Phi(0)/W(2) for complete flux expulsion.
- Observed increasing vortex density above B(m) with a near-linear field dependence.
- Found critical fields orders of magnitude lower than in bulk superconductors.
Conclusions:
- Thin-film superconducting devices require narrow wires to minimize vortex-induced noise.
- The study provides critical insights for designing low-noise superconducting electronics.