Possible Indications of Electronic Inhomogeneities in Superconducting Nanowire Detectors

TL;DR

This study investigates the voltage transition behavior in superconducting NbTiN nanowires used for photon detection, suggesting intrinsic electronic inhomogeneities as a possible cause for observed steplike patterns.

Contribution

It introduces a thermal model considering electronic inhomogeneities to explain the steplike voltage transitions in disordered superconducting nanowires.

Findings

Steplike voltage transitions vary between samples.

Geometrical inhomogeneities do not account for the features.

Electronic inhomogeneities are a plausible explanation.

Abstract

The voltage-carrying state of superconducting NbTiN nanowires, used for single-photon detectors, is analyzed. Upon lowering the current, the wire returns to the superconducting state in a steplike pattern, which differs from sample to sample. Elimination of geometrical inhomogeneities, such as sharp corners, does not remove these steplike features. They appear to be intrinsic to the material. Since the material is strongly disordered, electronic inhomogeneities are considered as a possible cause. A thermal model, taking into account random variations of the electronic properties along the wire, is used as an interpretative framework.