Directional vortex motion guided by artificially induced mesoscopic potentials

Abstract

Rectangular pinning arrays of Ni dots define a potential landscape for vortex motion in Nb films. Magnetotransport experiments in which two in-plane orthogonal electrical currents are injected simultaneously allow one to select the direction and magnitude of the Lorentz force on the vortex lattice, thus providing the angular dependence of the vortex motion. The background dissipation depends on the angle at low magnetic fields, which is progressively smeared out with increasing field. The periodic potential locks in the vortex motion along channeling directions. Because of this, the vortex-lattice direction of motion is up to 85 o away from the applied Lorentz force direction.

Vortex ratchet reversal: Role of interstitial vortices

“…This type of channeling has been seen elsewhere. [17][18][19] We emphasize that the ratchet reversal is well established experimentally in superconducting films with arrays of structurally asymmetric pinning sites, but its origin is very controversial. There are different models used to explain the 174507-3 presence of this reversal.…”

Structural transitions and dynamical regimes for directional locking of vortices and colloids driven over periodic substrates

“…In addition to the colloidal work, symmetry locking effects have been further studied for superconducting vortices in numerical simulations [22,23] and have also been observed experimentally [22,24,25,26]. For systems in which the particles are strongly interacting, dynamical symmetry locking effects can occur even when the particles are moving over a random substrate provided that the particle-particle interactions are strong enough to overcome the randomness of the substrate and produce a triangular ordering of the moving particles [27,28].…”

Commensurability Effects in Superconducting Nb Films with Quasiperiodic Pinning Arrays

“…Recent progress in the fabrication of nanostructures provided the possibility to realize superconducting thin films which contain artificial defects as pinning sites with well-defined size, geometry and spatial arrangement. In particular, artificially produced periodic arrays of submicron holes (antidots) [5,6,7,8] and magnetic dots [9,10,11,12] as pinning sites have been intensively investigated during the last years, to address the fundamental question how vortex pinning -and thus the critical current density j c in superconductors -can be drastically increased.In this context, it has been shown that a very stable vortex configuration, and hence an enhancement of the critical current I c occurs when the vortex lattice is commensurate with the underlying periodic pinning array. This situation occurs in particular at the so-called first matching field B 1 = Φ 0 /A, i.e., when the applied field B corresponds to one flux quantum Φ 0 = h/2e per unit-cell area A of the pinning array.…”