Superconducting properties of polycrystalline Nb nanowires templated by carbon nanotubes

TL;DR

This study demonstrates the fabrication of polycrystalline Nb nanowires via sputter-coating carbon nanotubes, revealing high critical currents and thermally activated phase slips consistent with LAMH theory, with quantum slips suppressed.

Contribution

It introduces a method to produce Nb nanowires with high critical currents and characterizes their superconducting behavior, confirming thermally activated phase slips dominate.

Findings

Wires are polycrystalline with ~5 nm grains.

Critical current exceeds 10^7 A/cm^2 for thicker wires.

Resistance behavior aligns with LAMH theory, quantum slips suppressed.

Abstract

Continuous Nb wires, 7-15 nm in diameter, have been fabricated by sputter-coating single fluorinated carbon nanotubes. Transmission electron microscopy revealed that the wires are polycrystalline, having grain sizes of about 5 nm. The critical current of wires thicker than ~12 nm is very high (10^7 A/cm^2) and comparable to the expected depairing current. The resistance versus temperature curves measured down to 0.3 K are well described by the Langer-Ambegaokar-McCumber-Halperin (LAMH) theory of thermally activated phase slips. Quantum phase slips are suppressed.