Investigation of dark counts in innovative materials for superconducting nanowire single-photon detector applications

The phenomenon of dark counts in nanostripes of different superconductor systems such as high-temperature superconducting YBa2Cu3O7-x and superconductor/ferromagnet hybrids consisting of either NbN/NiCu or YBa2Cu3O7- x/L0.7Sr0.3MnO3 bilayers have been investigated. For NbN/NiCu the rate of dark-count transients have been reduced with respect to pure NbN nanostripes and the events were dominated by a single vortex entry from the edge of the stripe. In the case of nanostripes based on YBa2Cu3O7-x, we have found that thermal activation of vortices was also, apparently, responsible for triggering dark-count signals.