Mesoscopic Conductance Oscillations in Superconducting Nanoparticle Films

Abstract

We have studied electronic transport in disordered granular films fabricated by sintering superconducting Nb nanoparticles. Measurements of resistance versus bias voltage and magnetic field reveal zero-bias and zerofield minima, respectively, as well as superimposed conductance oscillations. We attribute these observations to reflectionless tunneling. Robust observation of such phenomena in a macroscopic system is remarkable given their mesoscopic origin. It is enabled by the ability of the present "bottom-up" approach to balance counterveiling considerations: sufficient disorder to induce both elastic scattering and interference combined with restricted averaging to limit dephasing.