Nanostructured Superconductors With Asymmetric Pinning Potentials: Vortex Ratchets

Ratchets formed from spatially asymmetric confining potentials can rectify an oscillatory driving force and generate directed motion. Such devices can probe the fundamental nature of particle transport in nanoscale systems, both solid state and biological. Vortices in superconductors form an ideal system for exploring ratchet phenomena. Various techniques are available for producing nanostructured pinning landscapes that can provide tailored asymmetries for vortex ratchets. Progress in the theory and experimental implementations of vortex ratchets will be reviewed. In many cases, intervortex interactions in ratchet structures result in intriguing collective effects in the vortex transport, such as reversals in the sense of the rectification. Future vortex ratchet investigations may probe possible quantum mechanical ratchet effects, explore the dynamics of single vortices in ratchets, and test vortex devices based on ratchet phenomena.