The influence of the spatial asymmetry of the pinning potential on the
spectral composition of the voltage, induced in perforated superconducting Al
bridges by the injection of a sinusoidal bias current, was investigated. The
loss of the mirror symmetry of the pinning potential leads to the appearance of
even Fourier components in the induced voltage in the vicinity of the
superconducting phase transition line on the H-T diagram (H is the external
magnetic field, T is temperature). Artificially-introduced asymmetry for vortex
motion makes it possible to create low-resistive materials, in which
nonlinearity depends on the direction of injected electrical currents.Comment: 5 pages, 10 figure