Evidence for Macroscopic Quantum Tunneling of Phase Slips in Long One-Dimensional Superconducting Al Wires

TL;DR

This paper provides experimental evidence for macroscopic quantum tunneling of phase slips in long, ultra-thin superconducting aluminum wires, advancing understanding of quantum phenomena in reduced-dimensional superconductors.

Contribution

It demonstrates that phase slips in one-dimensional superconducting wires occur via quantum tunneling rather than thermal activation, resolving a long-standing controversy.

Findings

Voltage-current characteristics support quantum tunneling of phase slips.

Linear resistance measurements are consistent with quantum effects at low temperatures.

Behavior persists in magnetic fields well below the superconducting transition.

Abstract

Quantum phase slips have received much attention due to their relevance to superfluids in reduced dimensions and to models of cosmic string production in the Early Universe. Their establishment in one-dimensional superconductors has remained controversial. Here we study the nonlinear voltage-current characteristics and linear resistance in long superconducting Al wires with lateral dimensions $\sim$ 5 nm. We find that, in a magnetic field and at temperatures well below the superconducting transition, the observed behaviors can be described by the non-classical, macroscopic quantum tunneling of phase slips, and are inconsistent with the thermal-activation of phase slips.