DISORDER-INDUCED FLICKER NOISE IN HIGH-TC RF SUPERCONDUCTING QUANTUM MAGNETOMETERS

Low-frequency noise in a hysteric rf superconducting quantum interfere nce device (SQUID) originating from fluctuations of critical current o f a weak link is considered. Such noise can be due to trapping-detrapp ing processes within the tunnel barrier or to the presence of structur al defects with internal degrees of freedom in the surrounding of the weak link. The defects can switch between two (or more) metastable sta tes due to interaction with the thermal bath. On the other hand, elast ic (and electric) fields created by defects act upon the critical curr ent of the weak link inducing its fluctuations in time. Such noise is most important for high-T(c) SQUIDs at high enough temperatures when d efects are effectively interacting with the thermal bath. The dependen cies of the intensity and statistics of flicker noise on the SQUID's p arameters and operating regime are analyzed. It is shown that higher c orrelation functions of output voltage at a given driving current can provide some information on the mechanism of 1/f noise in rf SQUIDs.