Quantum fluctuations in ultranarrow superconducting nanowires

TL;DR

This study investigates how quantum fluctuations affect superconducting transitions in ultranarrow aluminum nanowires, revealing deviations from classical models and indicating a universal breakdown of zero resistance at small scales.

Contribution

It demonstrates that quantum fluctuations dominate in nanowires with diameters ≤15 nm, challenging classical thermally activated phase slip models and supporting a universal breakdown of superconductivity.

Findings

Wider $R(T)$ transitions in nanowires ≤15 nm than predicted by thermal models.

Observation of negative magnetoresistance in the thinnest samples.

Experimental results align with existing quantum fluctuation theories.

Abstract

Progressive reduction of the effective diameter of a nanowire is applied to trace evolution of the shape of superconducting transition $R(T)$ in quasi-one-dimensional aluminum structures. In nanowires with effective diameter $\leq$ 15 nm the $R(T)$ dependences are much wider than predicted by the model of thermally activated phase slips. The effect can be explained by quantum fluctuations of the order parameter. Negative magnetoresistance is observed in the thinest samples. Experimental results are in reasonable agreement with existing theoretical models. The effect should have a universal validity indicating a breakdown of zero resistance state in a superconductor below a certain scale.