Electron--phonon interaction-induced nonlinearity of the current--voltage characteristic of superconductor--normal-metal point contacts

The results of the first experimental observation of the appearance of an electron--phonon interaction (EPI) on the current--voltage characteristics (IVC) of a superconductor--normal-metal point contact are reported. Features, corresponding to the characteristic EPI energies in the contacting metals, appear on the dependences of the excess current on the voltage and derivatives of the IVC. A correlation between the absolute value of the excess current and the maximum intensity of the microcontact EPI function of a heterocontact in the normal state is noted