  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.
