Nonlinearity Response of High-Tc Superconductors

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Nonlinearity Response of High-Tc Superconductors

• Advisor Edmond Wong
• Members Samir Castillo
• Charles H.Y. Cheung
• Daniel Commins
• Dong Quach

Sponsor
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Background

• High temperature superconducting cuprates are
  desirable in superconducting RF filters and
  microwave circuits
• YBa2Cu3O7-d (YBCO) thin film Tc _at_ 93K Liquid
  nitrogen cooled
• Filters Low noise, sharp bandpass
• Small, compact size

Fig. 1 Voltage response for an ultra-sensitive
absolute field sensor1
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Project

• Observed nonlinear surface impedance dependence
  on microwave power
• Two theories
• Agassi et. al. Local heuristic theory dividing
  penetration depth fringes with bulk2
• Dahm et. al. Non-local empirical theory based
  on second-order approximation3

Fig. 2 Surface currents of YBCO superconducting
strip2
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Statement of Work

• Research the analytic models for the local and
  non-local theories.
• Model both theories using appropriate software
• Compare and evaluate the results from both
  theories.

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Progress
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Plans for next week

• Further study and understanding of local and
  non-local theories
• Identify theory assumptions
• Identify input/output variables
• Begin analytical study
• Determine analytical method
• Determine optimal modeling software

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References

• J Oppenländer et. al., Phys. Rev. B 63, 4511
  (2001)
• D Agassi, DE Oates, J. Supercond. Vol. 16, pp.
  905-911 (2003)
• T Dahm, DJ Scalapino, BA Wilemsen, J. Supercond.
  Vol. 12, pp. 339-342 (1999)