Magnetoresistance studies of homogenously disordered 3-dimensional NbN thin films

Abstract

We present magnetoresistance studies on a series of homogenously disordered 3-dimensional NbN thin films with disorder ranging from the moderately clean limit (k_Fl~10.12) to the extremely dirty limit where the superconducting ground state is completely destroyed (k_Fl~0.42). We find that for samples with k_Fl >1, the magnetoresistance is positive up to 12T and as disorder increases it decays more slowly with temperature. On the other hand, for samples with k_Fl< 1, we observe a peak in the magnetoresistance which vanishes at a temperature close to the pseudogap temperature of disordered superconducting samples. These observations are consistent with the idea of the disorder-driven non-superconducting state being comprised of pre-formed Cooper pairs.