Electron localization effects on the low-temperature high-field magnetoresistivity of three-dimensional amorphous superconductors

Abstract

he electrical resistivity ρ of three-dimensional amorphous superconducting films a-Mo3Si and a-Nb3Ge is measured in magnetic fields μ0H up to 30 T. At low temperatures and at magnetic fields above the upper critical field Hc2, ρ is temperature independent and decreases as a function of magnetic field. This field dependence is consistent with localization theory in the high-field limit [μ0H≫ħ/(4eLφ2), where Lφ is the phase-coherence length]. Above the superconducting transition temperature Tc, the temperature dependence of the conductivity is consistent with inelastic scattering processes which are destructive to the phase coherence for electron localization, thereby allowing estimates for Lφ(T). The Hall effect data on a-Mo3Si, in conjunction with the resistivity data, allow the determination of the carrier concentration and mean free path. The upper critical field is comparable to (in a-Mo3Si) and significantly larger than (in a-Nb3Ge) the Clogston-Chandrasekhar paramagnetic limit. This phenomenon is discussed in the context of electron localization.