PT Journal
AU Murphy, A
   Semenov, A
   Korneev, A
   Korneeva, Y
   Gol'tsman, G
   Bezryadin, A
TI Three temperature regimes in superconducting photon detectors: quantum, thermal and multiple phase-slips as generators of dark counts
SO Sci. Rep.
JI Sci. Rep.
PY 2015
BP 10174 (1 to 10)
VL 5
DI 10.1038/srep10174
DE SPD; SSPD; SNSPD
AB We perform measurements of the switching current distributions of three w approximately 120 nm wide, 4 nm thick NbN superconducting strips which are used for single-photon detectors. These strips are much wider than the diameter of the vortex cores, so they are classified as quasi-two-dimensional (quasi-2D). We discover evidence of macroscopic quantum tunneling by observing the saturation of the standard deviation of the switching distributions at temperatures around 2 K. We analyze our results using the Kurkijarvi-Garg model and find that the escape temperature also saturates at low temperatures, confirming that at sufficiently low temperatures, macroscopic quantum tunneling is possible in quasi-2D strips and can contribute to dark counts observed in single photon detectors. At the highest temperatures the system enters a multiple phase-slip regime. In this range single phase-slips are unable to produce dark counts and the fluctuations in the switching current are reduced.
ER