Emergence of Quantum Phase-Slip Behaviour in Superconducting NbN Nanowires: DC Electrical Transport and Fabrication Technologies

TL;DR

This study develops and characterizes niobium nitride superconducting nanowires with controlled quantum phase-slip behavior, demonstrating fabrication methods and electrical properties crucial for quantum device applications.

Contribution

It introduces three fabrication techniques for superconducting nanowires and demonstrates control over quantum phase-slip phenomena in NbN nanowires.

Findings

Nanowires exhibit diverse behaviors including phase-slip centers and zero conductance.

Critical voltages up to 5 mV observed, larger than previous reports.

Quantum fluctuations influence the prominence of phase-slip effects.

Abstract

Superconducting nanowires undergoing quantum phase-slips have potential for impact in electronic devices, with a high-accuracy quantum current standard among a possible toolbox of novel components. A key element of developing such technologies is to understand the requirements for, and control the production of, superconducting nanowires that undergo coherent quantum phase-slips. We present three fabrication technologies, based on using electron-beam lithography or neon focussed ion-beam lithography, for defining narrow superconducting nanowires, and have used these to create nanowires in niobium nitride with widths in the range of 20-250 nm. We present characterisation of the nanowires using DC electrical transport at temperatures down to 300 mK. We demonstrate that a range of different behaviours may be obtained in different nanowires, including bulk-like superconducting properties with critical-current features, the observation of phase-slip centres and the observation of zero conductance below a critical voltage, characteristic of coherent quantum phase-slips. We observe critical voltages up to 5 mV, an order of magnitude larger than other reports to date. The different prominence of quantum phase-slip effects in the various nanowires may be understood as arising from the differing importance of quantum fluctuations. Control of the nanowire properties will pave the way for routine fabrication of coherent quantum phase-slip nanowire devices for technology applications.