Negative magnetoresistance of ultra-narrow superconducting nanowires in the resistive state

TL;DR

This paper introduces a phenomenological model explaining negative magnetoresistance in narrow superconducting nanowires by considering phase slip fluctuations and their associated quasi-normal regions, accounting for experimental observations.

Contribution

The model provides a new explanation for negative magnetoresistance in superconducting nanowires based on phase slip dynamics and quasiparticle relaxation effects.

Findings

Negative magnetoresistance occurs in certain magnetic field ranges.

Quasi-normal regions influence the effective resistance.

Model aligns qualitatively with experimental data.

Abstract

We present a phenomenological model qualitatively explaining negative magnetoresistance in quasi-one-dimensional superconducting channels in the resistive state. The model is based on the assumption that fluctuations of the order parameter (phase slips) are responsible for the finite effective resistance of a narrow superconducting wire sufficiently close to the critical temperature. Each fluctuation is accompanied by an instant formation of a quasi-normal region of the order of the non-equilibrium quasiparticle relaxation length 'pinned' to the core of the phase slip. The effective time-averaged voltage measured in experiment is a sum of two terms. First one is the conventional contribution linked to the rate of the fluctuations via the Josephson relation. Second term is the Ohmic contribution of this quasi-normal region. Depending on material properties of the wire, there might be a range of magnetic fields where the first term is not much affected, while the second term is effectively suppressed contributing to the experimentally observed negative magnetoresistance.