Vortex Fluctuations in High-Tc Films: Flux Noise Spectrum and Complex Impedance

Abstract

The flux noise spectrum and complex impedance for a 500 Å thick YBCO film are measured and compared with predictions for two dimensional vortex fluctuations. It is verified that the complex impedance and the flux noise spectra are proportional to each other, that the logarithm of the flux noise spectra for different temperatures has a common tangent with slope $\approx -1$, and that the amplitude of the noise decreases as $d^{-3}$, where $d$ is the height above the film at which the magnetic flux is measured. A crossover from normal to anomalous vortex diffusion is indicated by the measurements and is discussed in terms of a two-dimensional decoupling.

arXiv comment5 pages including 4 figures in two columns, to appear in Phys. Rev. Lett

References in corpus (4)

• 1/ω-flux-noise and dynamical critical properties of two-dimensional XY-models
• Flux noise in high-temperature superconductors
• Flux noise and Fluctuation conductivity in Unfrustrated Josephson Junction Arrays
• Flux-noise spectra around the Kosterlitz-Thouless transition for two-dimensional superconductors

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• Nonequilibrium steady states of driven magnetic flux lines in disordered type-II superconductors
• Fluctuation-dissipation theorem and flux noise in overdamped Josephson junction arrays
• Comment on ``Loss of Superconducting Phase Coherence in YBa_2Cu_3O_7 Films: Vortex-Loop Unbinding and Kosterlitz-Thouless Phenomena''
• Splitting of the superconducting transition in the two weakly coupled 2D XY models
• Anomalous dynamic response in the two-dimensional lattice Coulomb gas model: Effects of pinning