Magnetic dependence of the critical and persistent current of asymmetric superconducting rings

The obtained periodic magnetic-field dependencies of the critical current, measured in opposite directions on asymmetric superconducting aluminum rings, allow to explain observed earlier quantum oscillations of a dc voltage as a result of alternating current rectification. It is found, that the high efficiency of the rectification of both individual rings and ring systems is connected to a hysteresis of the current-voltage characteristics. The asymmetry of the current-voltage characteristics providing the rectification effect is due to the relative shifts of the magnetic dependencies of the critical current measured in opposite directions. This shift means that position of the critical current minimums does not correspond to n + 0.5 magnetic flux quantum which is in the direct contradiction with measurement results of the Little-Parks resistance oscillations. Despite of this contradiction the amplitude of the critical current anisotropy oscillations and its variations with temperature correspond to expected amplitude of the persistent current oscillations and to its variations with temperature.