Excess conductivity in high temperature superconductors
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Answer:
The excess electrical conductivity, Delta sigma , above Tc in single-phase (within 4%) Ba2LnCu3O7- delta compounds, with Ln=Y, Ho and Sm, has been measured in the reduced temperature range 5*10-4<or approximately= epsilon <or approximately=1; this extends previous results almost one order of magnitude closer to Tc. This allows the authors to observe, for the first time, four different Delta sigma ( epsilon ) regions, with different critical exponents. These regions are analysed in terms of the Aslamazov-Larkin (AL) theory for thermal fluctuations in BCS superconductors and also using some dynamical scaling ideas. The results suggest that the Ginzburg-Landau mean-field region is located in the high-temperature range. In that case, the corresponding critical exponent is of the order of -1/2, in agreement with 3D AL superconductivity, although the strong intrinsic anisotropy, the polycrystallinity and the local defects of the samples may cause the disagreement with the AL model observed for the amplitude of the fluctuation effects.
Answer:
Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor.