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.