Linewidth of Relaxation Oscillations of a Shunted Superconducting Point Contact
When a superconducting weak link is shunted with a very small resistor and fed with a constant-current source the Josephson oscillation can be very nearly sinusoidal, corresponding to constant-voltage bias of the weak link. However, there is an inductance L o of the loop containing the weak link and the resistor. If L 0>Φ0/2πi c where Φ0 is the flux quantum and i c the critical current, relaxation oscillations occur. These oscillations correspond roughly to the charging of L 0 to a current i≃ic followed by a sudden switch of some number N of flux quanta across the weak link, reducing the current to some lower value. We have observed the spectrum of these oscillations as a function of temperature and find that the character of the spectrum changes periodically with a period corresponding to ic(T)L0=Φ0
KeywordsCritical Current Weak Link Relaxation Oscillation Flux Quantum Bias Voltage Versus
Unable to display preview. Download preview PDF.