Weak localization, fluctuation, and superconductivity in thin Nb films and wires

Abstract

Weak localization, fluctuation conductivity, and related problems have been investigated based on a comprehensive set of experiments on transition metal Nb films and wires. The temperature 0 dependence of the inelastic scattering rate 1/~& of films with various thicknesses (25-80 A), estimated from magnetoresistance data above T"is well fitted to a function of Co+C& T+C3T'. The coe%cient C& is in excellent quantitative agreement with the theoretical prediction of the electronelectron scattering mechanism for two-dimensional dirty metals. The coe5cient C3 shows no thickness dependence and is in semiquantitative agreement with theories of three-dimensional electronphonon scattering mechanisms. The upper critical field of thin Nb wires with a width of less than a 1000 A exhibits unconventional temperature dependence close to T, . We also discuss this behavior.

Flux flow properties of niobium thin films in clean and dirty superconducting limits

“…Two very different micro- scopic mechanics are revealed with the τ qp (T )dependence for both superconducting limits. For "dirty" niobium films, quasiparticles lifetime doesn't change much with temperature and lays in the range 30−50 ps, this order of magnitude being in accordance with data obtained from magnetoconductance measurements 21 and photonic N b detectors 22 (figure7). This order of magnitude is also compatible with a simple calculation considering that vortex motion is characterised by pair breaking upstream from the core and by quasiparticles recombinaison downstream.…”

Superconductivity enhancement in thin films of niobium in superconducting double-barrier structures

“…5 and 6. In our experiment ⌫ in ϭ10 Ϫ2 Ӷ1 at in ϭ5ϫ10 Ϫ10 s for Nb at Tϭ7 K. 13 The substitution of the experimental ⌫ in to the calculation 5 gives a very small enhancement of (⌬ЈϪ⌬ B ) ͑the dash-dotted line in Fig. 2͒, which is less than the experimental one for VϭV ϩ .…”

“…At EϪ⌬Јӷ⌬Ј, in (E) is the same as the electron-phonon relaxation time in normal metal, in0 ϭ5ϫ10 Ϫ10 s at Tϭ7 K for Nb. 13 ͓The inelastic relaxation of the quasiparticles, injected to the interlayer of Nb Ј, goes through electron-electron and electron-phonon interactions ( in Ϫ1 ϭ e-e Ϫ1 ϩ e-ph Ϫ1 ), but in the case of tunnel injection ͑see estimations in Refs. 14-16͒ the electron-electron interaction is small in the Nb interlayer of SDBS's ( in Ϸ e-ph ).͔ The numerical calculation of the gap in the interlayer is made on the basis of the quasiparticle balance model: The number of quasiparticles injected into the interlayer ͑from the first electrode͒ must be equal to the total number of qua-siparticles extracted from it ͑to the second electrode͒ and quasiparticles, relaxed to the Fermi level in the interlayer.…”

Fractional Little-Parks effect observed in a topological superconductor

“…In fact, its rapidly decaying behavior at finite magnetic field resembles that of weak localization, known to be present in metals with sizable spin-orbit interaction [54]. Observations of the localization effect in superconductors have also been reported [55][56][57]. At any rate, this spike-like feature is not likely to be related to the magnetic flux quantization in the ring structure.…”