Nonlinear properties of Nb3Sn superconducting point contacts

An experimental investigation was made of superconducting point contacts (SPC's), made of the hightemperature superconductor Nb3Sn, in external microwave fields. It was found that under nonequilibrium conditions these SPC's had a high degree of nonlinearity which made it possible to observe current steps corresponding to harmonics of the external radiation frequency at voltages exceeding the limiting value for these SPC's. Maximum frequency multiplication up to 4.2 × 1012 Hz was recorded for an 8.9 × 109 Hz signal and up to 5 × 1012 Hz for a 7.8 × 1010 Hz signal. Investigations were made of the subharmonic structure of the current-voltage characteristics of SPC's in external microwave fields. Mixing of the microwave radiation with the contact self-radiation was observed experimentally at gap singularities.