Vortex-induced negative magnetoresistance and peak effect in narrow superconducting films

TL;DR

This study uses the Ginzburg-Landau model to analyze how narrow superconducting films exhibit unusual magnetic field-dependent transport properties, including nonmonotonic critical current and magnetoresistance due to vortex dynamics.

Contribution

It demonstrates the nonmonotonic dependence of critical current and magnetoresistance on magnetic field in narrow superconducting films, linking vortex behavior to observed experimental phenomena.

Findings

Critical current I_c(H) shows minima and maxima due to vortex effects.

Magnetoresistance R(H) exhibits peaks and dips related to vortex hopping.

Finite length causes periodic variations in I_c(H) and R(H).

Abstract

In framework of Ginzburg-Landau model it is shown that narrow superconducting film with width w ~ 3-8 \xi(T) (\xi(T) is a temperature dependent coherence length) exhibits unusual transport properties. In the absence of bulk pinning its critical current Ic nonmonotonically depends on perpendicular magnetic field H and has one minima (dip) and one maxima (peak) at some magnetic fields. At currents I << Ic(H) the finite magnetoresistance R(H) of such a samples due to thermo-activated vortex hopping via edge barriers also shows both local maxima(peak) and minima(dip) nearly at the same magnetic fields. In narrower films such an effect is absent due to absence of the vortices and in wider films the effect is weaker due to increased vortex-vortex interaction. Finite length of the film produces additional periodic variation in both Ic(H) and R(H) because of discrete change in the number of the vortices, which is superimposed on the above mentioned nonmonotonic dependence. The obtained results are directly related to many experiments on narrow superconducting films/bridges where such a nonmonotonic dependencies Ic(H) and R(H) were observed.