Topology controlled phase coherence and quantum fluctuations in superconducting nanowires

TL;DR

This paper investigates how topology influences phase coherence and quantum fluctuations in superconducting nanowires, revealing a phase diagram with distinct superconducting and fluctuation-dominated phases depending on wire cross section.

Contribution

It introduces a model analyzing the effects of phase fluctuations and quantum phase slips in superconducting nanowires with restricted phase fluctuations, mapping out a zero-temperature phase diagram.

Findings

Existence of a truly superconducting phase depending on wire cross section

Identification of short-scale superconductivity phases with different robustness

Power-law decay of supercurrent in certain fluctuation-dominated phases

Abstract

Superconducting properties of metallic nano-wires may strongly depend on specific experimental conditions. Here we consider a setup where superconducting phase fluctuations are restricted at one point inside the wire and equilibrium supercurrent flows along the wire segment of an arbitrary length $L$. Low temperature physics of this structure is essentially determined, on one hand, by smooth phase fluctuations and, on the other hand, by quantum phase slips. The zero temperature phase diagram is controlled by the wire cross section and consists of a truly superconducting phase and two different phases where superconductivity can be observed only at shorter length scales. One of the latter phases exhibits more robust short-scale superconductivity whereas another one demonstrates a power-law decay of the supercurrent with increasing $L$ already at relatively short scales.