dc SQUIDs based on double-barrier Nb/Al/AlOx/Al/AlOx/Al/Nb junctions (DBSQs) have been fabricated and tested for the first time. The current–voltage curves have been measured at temperatures down to 1.4 K. The critical current, Ic, dependence on the temperature T is partially described by the existing microscopic theory for double-barrier junctions. A peculiar initial decrease of Ic with decreasing T was observed, which can qualitatively be explained if trapping events are taken into account. We have investigated the effective resistance, Reff, determining the DBSQ dynamics. The noise properties of the DBSQ have been studied using a two-stage SQUID based system, and were compared with equivalent damped and underdamped single-barrier based SQUIDs. The best white noise level measured on a DBSQ (3.3 μΦ0/Hz1/2) is larger than the noise of an equivalent single-barrier SQUID (1.3 μΦ0/Hz1/2).
|Number of pages||8|
|Publication status||Published - 2000|
- Two-stage system
- Double-barrier junction