Differences in the effects of turns and constrictions on the resistive response in current-biased superconducting wire after single photon absorption

TL;DR

This study investigates how turns and constrictions in superconducting wires influence their ability to detect single photons, revealing that constrictions enhance detection across various energies while turns mainly improve detection of low-energy photons.

Contribution

It provides a detailed analysis of how geometrical features like turns and constrictions affect the resistive response and photon detection efficiency in current-biased superconducting wires.

Findings

Constrictions improve detection of photons with various energies.

Turns increase detection ability mainly for low-energy photons.

Voltage pulse amplitude varies with photon absorption location.

Abstract

We study how turns and constrictions affect the resistive response of the superconducting wire after instant in time and local in space heating, which models the absorption of the single photon by the wire. We find that the presence of constriction favors detection of photons of various energies but the presence of turn increases only ability to detect relatively "low" energy photons. The main reason is that in case of constriction the current density is increased over whole length and width of the constriction while in case of the turn the current density is enhanced only near the inner corner of the turn. It results in inhomogeneous Joule heating near the turn and worsens the conditions for appearance of the normal domain at relatively small currents when the "high" energy photons already could create normal domain in straight part of the wire. We also find that the amplitude of the voltage pulse depends on the place where the photon is absorbed. It is the smallest one when photon is absorbed near the turn and it is the largest one when photon is absorbed near the constriction. This effect comes from the difference in resistance of constriction and the turn in the normal state from the resistance of the rest of the wire.