Distribution of flux-pinning energies in YBa 2 Cu 3 O 7 − δ and Bi 2 Sr 2 CaCu 2 O 8 + δ from flux noise

摘要: The spectral density of the magnetic flux noise measured in high-temperature superconductors low fields scales approximately as inverse frequency and increases with temperature. We use temperature dependence to determine pinning energies individual vortices thermal equilibrium. distribution peaks below 0.1 eV ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ near 0.2 ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$. power is proportional ambient field, indicating that vortex motion uncorrelated.