Quantum Phase Slips in 6 mm Long Niobium Nanowire

Area of Science:

• Condensed matter physics
• Materials science

Background:

• Superconducting transitions in nanowires are crucial for quantum electronics.
• Quantum phase slip (QPS) is a phenomenon affecting superconductivity in low-dimensional systems.

Purpose of the Study:

• To investigate the superconducting transition in niobium (Nb) nanowires.
• To explore the role of quantum phase slip (QPS) in nanowire resistance behavior.
• To unify previously exclusive experimental observations of QPS.

Main Methods:

• Fabrication of four niobium nanowires with varying cross-sectional dimensions.
• Low-temperature transport measurements using a 5 nA excitation current.
• High bias excitation current measurements to observe resistance switching.
• Analysis of resistance behavior as a function of temperature.

Main Results:

• A residual resistance tail, consistent with QPS, was observed in the thinnest Nb wire down to 50 mK (7.7% of Tc).
• Resistance measurements at high bias current revealed discrete, sub-normal state values.
• These discrete resistance values exhibited QPS-like temperature dependence, forming parallel curves.
• The coexistence of both QPS-like resistance tails and jumps was observed in the same wire.

Conclusions:

• The study provides unified evidence for quantum phase slip (QPS) in niobium nanowires.
• The findings reconcile previous experiments that exclusively reported either resistance tails or jumps.
• This research advances the understanding of quantum phenomena in superconducting nanostructures.