Abstract
The photon count rate (PCR) of superconducting single-photon detectors made of films shaped as a 2--wide strip and a 115-nm-wide meander strip line is studied experimentally as a function of the dc biasing current at different values of the perpendicular magnetic field. For the wide strip, a crossover current is observed, below which the PCR increases with an increasing magnetic field and above which it decreases. This behavior contrasts with the narrow meander, for which no crossover current is observed, thus suggesting different photon-detection mechanisms in the wide and narrow strips. Namely, we argue that in the wide strip the absorbed photon destroys superconductivity locally via the vortex-antivortex mechanism for the emergence of resistance, while in the narrow meander superconductivity is destroyed across the whole strip line, forming a hot belt. Accordingly, the different photon-detection mechanisms associated with vortices and the hot belt determine the qualitative difference in the dependence of the PCR on the magnetic field.
- Received 3 October 2019
- Revised 28 November 2019
- Accepted 29 December 2019
DOI:https://doi.org/10.1103/PhysRevApplied.13.024011
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