Guiding of vortices and ratchet effect in superconducting films with asymmetric pinning potential

Abstract: Two-dimensional vortex dynamics in a ratchet washboard planar pinning potential (PPP) in the presence of thermal fluctuations is considered on the basis of a Fokker-Planck equation. Explicit expressions for two new nonlinear anisotropic voltages (longitudinal and transverse with respect to the current direction) are derived and analyzed. The physical origin of these odd (with respect to magnetic field or transport current direction reversal) voltages is caused by the interplay between the even effect of vortex guiding and the ratchet asymmetry. Both new voltages are going to zero in the linear regimes of the vortex motion (i.e. in the thermally activated flux flow (TAFF) and ohmic flux flow (FF) regimes) and have a bump-like current or temperature dependence in the vicinity of the highly nonlinear resistive transition from the TAFF to the FF.