Electron phase-breaking time in ultra-thin Nb films

Abstract. Here we study the temperature dependences of the electron phase-breaking time τϕ in ultra-thin superconducting niobium (Nb) films. In Nb films, passivated with a layer of silicon (Si), the observed temperature dependence of the phase-breaking time is τ_ϕ ~ Т^-2.5, is resembling the electron-phonon scattering. However, in the uncovered Nb films, we observe the saturation of τϕ at low temperatures, which may be a signature of the surface magnetic disorder, present in native Nb oxide on the film surface.