IVC studies for <i>S–c–N</i> contacts based on the amorphous superconductor Zr2Ni

The current–voltage characteristics (IVC) of the S–c–N contacts, formed between Zr2Ni and a normal metal (Cu, Ag) and having a resistance from a few tenths of an ohm to several tens of ohms, are measured at a temperature below the superconducting transition temperature Tc ≈ 2.5 K. A considerable increase in IVC nonlinearity is observed both upon a decrease in temperature and upon a reduction of the contact resistance. In the latter case, the IVC acquires a singularity of the the voltage-jump at a certain critical value of the current. The observed singularity can be explained by the generation of Abrikosov vortices upon the attainment of a critical current and by the transition of the contact region to the resistive state. The qualitative difference between the IVC of low-resistivity point contacts and high-resistivity ones is associated with the effect of the contact size on the vortex kinetics. A relation between the values of critical parameters of a superconductor and the position of singular points on IVC of the contacts under investigation is also established.

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