Small angle neutron scattering from superconductors

Small angle neutron scattering is a well known technique for studying the properties of solids at small but finite energies and momenta. In this work it has been applied to the study of the low energy properties of superconductors. The low transition temperature superconductors niobium and lead and the high transition temperature superconductor Y(_1)Ba(_2)Cu(_3)O(_7) have been investigated. The results indicate a temperature dependent excess scattering of around 150 mbam/sr/atom from Y(_1)Ba(_2)Cu(_3)O(_7) at wavevectors q of around 0.03 Å and an energy of less than 30 µeV. No such effect was observable, even at much lower wavevectors (q around 0.004 Å (^-1) in the low transition temperature superconductor niobium. However, a drop in transmission of a niobium sample at T(_c) indicates an increase in cross section of 71 ± 15 mbarn/atom. No simple explanation for these effects has been found.