Spatially-dependent sensitivity of superconducting meanders as single-photon detectors

TL;DR

This study investigates how the position of photon absorption affects the detection mechanism in superconducting meander-based single-photon detectors, revealing spatial sensitivity variations due to current crowding effects.

Contribution

It introduces a detailed theoretical analysis of spatially-dependent photon detection in superconducting meanders using the time-dependent Ginzburg-Landau theory, highlighting the impact of geometry on detection.

Findings

Photon absorption near the inner corner triggers vortex nucleation without detection.

Detection occurs only when photons hit away from the corner, causing vortex-antivortex pairs.

Current crowding significantly influences the detector's sensitivity based on photon position.

Abstract

The photo-response of a thin current-carrying superconducting stripe with a 90-degree turn is studied within the time-dependent Ginzburg-Landau theory. We show that the photon acting near the inner corner (where the current density is maximal due to the current crowding [J. R. Clem and K. K. Berggren, Phys. Rev. B {\bf 84}, 174510 (2011)]) triggers the nucleation of superconducting vortices at currents much smaller than the expected critical one, but {\it does not} bring the system to a higher resistive state and thus remains undetected. The transition to the resistive state occurs only when the photon hits the stripe away from the corner due to there uniform current distribution across the sample, and dissipation is due to the nucleation of a kinematic vortex-antivortex pair near the photon incidence. We propose strategies to account for this problem in the measurements.