Numerical analysis of detection-mechanism models of SNSPD

TL;DR

This paper develops a theoretical model to analyze photon detection mechanisms in SNSPDs, strongly supporting the vortex-crossing model through calculations and comparison with experimental data.

Contribution

The paper introduces a simplified yet effective model based on quasi-particle dynamics to distinguish between different detection mechanisms in SNSPDs, favoring the vortex-crossing scenario.

Findings

Vortex-crossing is the primary detection mechanism supported by the model.

The model aligns well with experimental data on SNSPD detection.

Detection criteria based on quasi-particle evolution differentiate mechanisms.

Abstract

The microscopic mechanism of photon detection in superconducting nanowire single-photon detectors is still under debate. We present a simple, but powerful theoretical model that allows us to identify essential differences between competing detection mechanisms. The model is based on quasi-particle multiplication and diffusion after the absorption of a photon. We then use the calculated spatial and temporal evolution of this quasi-particle cloud to determine detection criteria of three distinct detection mechanisms, based on the formation of a normal conducting spot, the reduction of the effective depairing critical current below the bias current and a vortex-crossing scenario, respectively. All our calculations as well as a comparison to experimental data strongly support the vortex-crossing detection mechanism by which vortices and antivortices enter the superconducting strip from the edges and subsequently traverse it thereby triggering the detectable normal conducting domain. These results may therefore help to reveal the microscopic mechanism responsible for the detection of photons in superconducting nanowires.