On the d.c. voltage across a double point contact between two superconductors at zero applied d.c. current in situations in which the junction is in the resistive region due to the circulating current of flux quantization

Abstract

The relationship between current, voltage and magnetic field as a function of temperature for a double point contact between two superconductors has been investigated in more detail. Special attention has been given to its behaviour in the critical temperature region, in which the double junction is in the resistive-superconductive region due to the net circulating current (around the area between the contacts) which screens the magnetic field partially due to flux quantization. A d.c. voltage has been observed when no d.c. contact currents are applied. This voltage changes periodically as a function of an applied magnetic field of moderate strength. Double point contacts have been investigated with relatively small self-inductances and small critical currents in order to obtain a large critical temperature region in which the voltage oscillations at zero applied d.c. current can be observed. It appears that the presence of a small electromagnetic field in the radio frequency range is responsible for the observed energy dissipation, as a rectification process takes place in the double junction.