Vortex jets generated by edge defects in current-carrying superconductor thin strips

Abstract

At sufficiently large transport currents I tr , a defect at the edge of a superconducting strip acts as a gate for the vortices entering into it. These vortices form a jet, which is narrow near the defect and expands due to the repulsion of vortices as they move to the opposite edge of the strip, giving rise to a transverse voltage V ⊥ . Here, relying upon the equation of vortex motion under competing vortex-vortex and I tr -vortex interactions, we derive the vortex jet shapes in narrow (ξ ≪ w λ eff ) and wide (w ≫ λ eff ) strips [ξ : coherence length, w: strip width, λ eff : effective penetration depth]. We predict a nonmonotonic dependence V ⊥ (I tr ) which can be measured with Hall voltage leads placed on the line V 1 V 2 at a small distance l apart from the edge defect and which changes its sign upon l −l reversal. For narrow strips, we compare the theoretical predictions with experiment, by fitting the V ⊥ (I tr , l) data for 1 µm-wide MoSi strips with single edge defects milled by a focused ion beam at distances l = 16-80 nm from the line V 1 V 2 . For wide strips, the derived magnetic-field dependence of the vortex jet shape is in line with the recent experimental observations for vortices moving in Pb bridges with a narrowing. Our findings are augmented with the time-dependent Ginzburg-Landau simulations which reproduce the calculated vortex jet shapes and the V ⊥ (I tr , l) maxima. Furthermore, with increase of I tr , the numerical modeling unveils the evolution of vortex jets to vortex rivers, complementing the analytical theory in the entire range of I tr .