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

Abstract

In the framework of the Ginzburg-Landau model, it is shown that narrow superconducting films with width w≃3–8ξ(T) [ξ(T) is a temperature-dependent coherence length] exhibit 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 sample due to thermoactivated 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. The finite length of the film produces additional periodic variation in both Ic(H) and R(H) because of discrete changes 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 nonmonotonic dependencies Ic(H) and R(H) were observed.

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