Fabrication and properties of longitudinal and transverse current rectifier devices based on superconducting films with arrays of nanodefects

Superconducting rectifiers have been fabricated by electron beam lithography, sputtering and ion etching techniques. The rectifiers are made growing Nb films on top of arrays of sub- micrometric Ni triangles. In this device, in the superconducting mixed state, injecting an input ac current yields an output dc voltage. This effect is due to the motion of the vortex lattice on periodic asymmetric pinning potentials. The vortex lattice dynamics follows ratchet effect behavior. The device shows two ratchet effects: Longitudinal and transverse. In the longitudinal ratchet effect the dc signal polarity could be switched increasing the applied magnetic field strength. Otherwise, the sign of the transverse effect does not change increasing the applied magnetic field.