Intrinsic detection efficiency of superconducting nanowire single photon detector in the modified hot spot model

Abstract

We theoretically study the dependence of the intrinsic detection efficiency (IDE) of superconducting single photon detector on the applied current I and magnetic field H. We find that the current, at which the resistive state appears in the superconducting film, depends on the position of the hot spot (region with suppressed superconductivity around the place where the photon has been absorbed) with respect to the edges of the film. It provides inevitable smooth dependence IDE(I) when IDE ∼ 0.05 − 1 even for homogenous straight superconducting film and in the absence of fluctuations. When IDE 0.05 much sharper current dependence comes from the fluctuation assisted vortex entry to the hot spot located near the edge of the film. We find that weak magnetic field strongly affects IDE when the photon detection is connected with fluctuation assisted vortex entry (IDE≪ 1) and it weakly affects IDE when the photon detection is connected with the current induced vortex entry to the hot spot or nucleation of the vortex-antivortex pair inside the hot spot (IDE∼ 0.05 − 1).

Different Single-Photon Response of Wide and Narrow Superconducting MoxSi1−x Strips

“…Therefore the dependence PCR(I) should shift towards lower currents as it follows from Refs. 27,32 and resemble the evolution of DCR(I) with increasing B. However, since the minimal detection current cannot exceed the retrapping current, as at I < I r the growing normal domain cannot appear in the superconducting strip 5 , this shift is partially observed only for λ = 1550 nm.…”

Detection mechanism of superconducting nanowire single-photon detectors

“…(b) Position-dependence of the threshold current (I det in the figure) for different hotspots. The strip width w = 20 ξ GL is roughly equivalent to 100 nm (Reproduced with permission from [111]. c IOP Publishing.…”

Quasiparticle recombination in hotspots in superconducting current-carrying nanowires

“…This is indicated in figure 4 by a transition to the lower end ("end" point) of the relaxation curve. The question of whether vortices play a crucial role in the detection mechanism of SNSPDs has received great interest recently [5][6][7][22][23][24] . Vortex generation can be easily incorporated into our model by slightly modifying the end points of relaxation.…”