Reversible recovery of excess current in Y(Ho)–Ba–Cu–O–normal metal point contacts under high voltages

A polarity-dependent reversible change in the current–voltage characteristics between states corresponding to different values of the excess current I_exc is observed for bias voltages of several hundred millivolts in Ag-ReBa₂Cu₃O_7–x (Re = Y, Ho) point contacts in the current–carrying state. The observed effect has a high intensity (right up to a complete suppression or recovery of I_exc) and is not accompanied by a noticeable variation of the energy gap or the critical temperature in the point contact region. It is also established that the states with intermediate values of I_exc are stable for zero bias voltages across the point contacts, at least up to 110 K. It is assumed that the variation of I_exc and the coresponding modification of IVC are due to the oxygen migration processes induced by the electric field and current, resulting in a local variation of the superconducting parameters in the point-contact region.