Sign reversal of the flux-flow Hall effect in sputtered a-axis- and c-axis-oriented films of 1:2:3 superconducting cuprates

Rocking ratchets in nanostructured superconducting-magnetic hybrids

Two rectification mechanisms in vortex lattice dynamics in Nb films have been studied. These two effects are based on ratchet effects, that is, an ac driving force induces a net dc vortex flow. In our case, an input ac current applied to the Nb films, grown on top of arrays of Ni nanotriangles, yields an output dc voltage. These two rectification effects occur when the vortex lattice moves in periodic asymmetric potentials. These pinning potentials are induced by the array of Ni triangles. In one configuration (longitudinal effect) the driven force is applied perpendicular to the triangle reflection symmetry axis; in the second one (transverse effect) the input current is injected parallel to the triangle reflection symmetry axis. In the framework of the rocking ratchet mechanism, the appropriate Langevin equation allows us to model the experimental data, taking into account the vortex-vortex interaction.