Temperature-dependence of detection efficiency in NbN and TaN SNSPD
  We present systematic measurements of the temperature-dependence of detection efficiencies in TaN and NbN superconducting nanowire single-photon detectors. We have observed a clear increase of the cut-off wavelength with decreasing temperature that we can qualitatively describe with a temperature-dependent diffusion coefficient of the quasi-particles created after photon absorption. Furthermore, the detection efficiency at wavelengths shorter than the cut-off wavelength as well as at longer wavelengths exhibit distinct temperature dependencies. The underlying causes and possible consequences for microscopic detection models are discussed. 
Andreas Engel, Kevin Inderbitzin, Andreas Schilling, Robert Lusche,   Alexei Semenov, Heinz-Wilhelm H\"ubers, Dagmar Henrich...
cond-mat.supr-con physics.ins-det