Magnetic field enhancement of superconductivity in ultra-narrow wires

TL;DR

This study demonstrates that magnetic fields can enhance superconductivity in ultra-narrow MoGe and Nb wires by suppressing pair-breaking magnetic moments, with a developed microscopic theory explaining the observations.

Contribution

It introduces a microscopic theory explaining magnetic field-induced enhancement of superconductivity in ultra-narrow wires, highlighting surface magnetic moments as a key factor.

Findings

Magnetic fields enhance critical supercurrent in narrow wires.

Narrower wires show stronger magnetic field effects.

Surface magnetic moments are likely responsible for the phenomena.

Abstract

We study the effect of an applied magnetic field on sub-10nm wide MoGe and Nb superconducting wires. We find that magnetic fields can enhance the critical supercurrent at low temperatures, and does so more strongly for narrower wires. We conjecture that magnetic moments are present, but their pair-breaking effect, active at lower magnetic fields, is suppressed by higher fields. The corresponding microscopic theory, which we have developed, quantitatively explains all experimental observations, and suggests that magnetic moments have formed on the wire surfaces.