Understanding multiscale disorder in superconducting nanowire single photon detectors

TL;DR

This paper investigates how nanoscale disorder affects superconducting nanowire single-photon detectors by combining various measurement techniques to distinguish different physical processes and enable disorder engineering.

Contribution

It introduces a systematic approach to tune and analyze disorder effects in superconducting nanowire devices using combined experimental methods.

Findings

Disorder modifies the superconducting density of states and kinetic inductance.

Multiple resonant modes indicate electrodynamically distinct superconducting regions.

Different microwave loss mechanisms are identified and separated.

Abstract

Superconducting nanowire single-photon detectors are central to applications across quantum information science. Yet, their performance is limited by the effects of disorder and electrodynamic inhomogeneities that are not well understood. By combining DC transport, dark-count measurements, and bias-dependent microwave transmission spectroscopy in the presence of controlled nanoscale disorder introduced through helium-ion irradiation, we distinguish local instability-driven processes from intrinsic superconducting depairing and kinetic inductance nonlinearities. This approach enables systematic tuning of kinetic inductance, depairing currents, microwave dissipation, and mode structure within a single device. Bias- and temperature-dependent resonance shifts quantify disorder-induced modifications of the superconducting density of states through the nonlinear kinetic inductance, while the emergence of multiple resonant modes reveals the formation of electrodynamically distinct superconducting regions. Comparing depairing under current, field, and temperature isolates the dominant microwave loss mechanisms, separating vortex, quasiparticle, and two-level-system contributions, thus providing a robust multifunctional foundation for disorder engineering of superconducting nanowire detectors and resonators.