title: Three temperature regimes in superconducting photon detectors: quantum, thermal and multiple phase-slips as generators of dark counts.
abstract: We perform measurements of the switching current distributions of three w ≈ 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 Kurkijärvi-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.
authors.affiliation: Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Murphy
authors.affiliation: 1] Moscow State Pedagogical University, 1 Malaya Pirogovskaya, 119991 Moscow, Russia [2] Moscow Institute of Physics and Technology, 141700, Dolgoprudny, Moscow Region, Russia.
authors.forename: Alexander
authors.initials: A
authors.lastname: Semenov
authors.affiliation: 1] Moscow State Pedagogical University, 1 Malaya Pirogovskaya, 119991 Moscow, Russia [2] Moscow Institute of Physics and Technology, 141700, Dolgoprudny, Moscow Region, Russia.
authors.forename: Alexander
authors.initials: A
authors.lastname: Korneev
authors.affiliation: Moscow State Pedagogical University, 1 Malaya Pirogovskaya, 119991 Moscow, Russia.
authors.forename: Yulia
authors.initials: Y
authors.lastname: Korneeva
authors.affiliation: 1] Moscow State Pedagogical University, 1 Malaya Pirogovskaya, 119991 Moscow, Russia [2] National Research University Higher School of Economics, Moscow 101000, Russia.
authors.forename: Gregory
authors.initials: G
authors.lastname: Gol'tsman
authors.affiliation: Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Alexey
authors.initials: A
authors.lastname: Bezryadin