Dependence of Photon Detection Efficiency on Normal-State Sheet Resistance in Marginally Superconducting Films of NbN
Philipp Zolotov (National Research University Higher School of Economics (HSE University), LLC Superconducting Nanotechnology (Scontel))
Alexander Semenov (Moscow State Pedagogical University)
Alexander Divochiy (LLC Superconducting Nanotechnology (Scontel))
Gregory Goltsman (Moscow State Pedagogical University, FRC Institute of Applied Physics RAS, Nizhny Novgorod)
Nikita Romanov (LLC Superconducting Nanotechnology (Scontel), National Research University Higher School of Economics (HSE University))
T. M. Klapwijk (Kavli institute of nanoscience Delft, TU Delft - QN/Afdelingsbureau)
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Abstract
We present an extensive set of data on nanowire-type superconducting single-photon detectors based on niobium-nitride (NbN) to establish the empirical correlation between performance and the normal-state resistance per square. We focus, in particular, on the bias current, compared to the expected depairing current, needed to achieve a near-unity detection efficiency for photon detection. The data are discussed within the context of a model in which the photon energy triggers the movement of vortices i.e. superconducting dissipation, followed by thermal runaway. Since the model is based on the non-equilibrium theory for conventional superconductors deviations may occur, because the efficient regime is found when NbN acts as a marginal superconductor in which long-range phase coherence is frustrated.
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