Characterization of MoSi Superconducting Single-Photon Detectors in the Magnetic Field

We investigate the response mechanism of nanowire superconducting single-photon detectors (SSPDs) made of amorphous Mo x Si 1-x . We study the dependence of photon count and dark count rates on bias current in magnetic fields up to 113 mT at 1.7 K temperature. The observed behavior of photon counts is similar to the one recently observed in NbN SSPDs. Our results show that the detecting mechanism of relatively high-energy photons does not involve the vortex penetration from the edges of the film, and on the contrary, the detecting mechanism of low-energy photons probably involves the vortex penetration from the film edges.