Temperature dependence of the Josephson linewidth of resistively shunted double junction HTS SQUIDs

• Published in: IEEE transactions on applied superconductivity 2001-03, Vol.11 (1), p.1215-1218
• Main Authors: Peden, D.A., Hao, L., Macfarlane, J.C., Lee, R.A.M., Gallop, J.C.
• Format: Article
• Language: English
• Subjects: Applied sciences; Electrical resistance measurement; Electronics; Exact sciences and technology; Frequency measurement; Gold; High temperature superconductors; Josephson junctions; Resistors; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; SQUIDs; Superconducting devices; Temperature dependence; Temperature distribution; Thermal resistance
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/77.919568

Double Josephson junction HTS resistive SQUIDs have been fabricated using an on-chip shunt Au resistor across a gap in an YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// loop, providing a low shunt resistance of R/sub s/ /spl sim/26 /spl mu//spl Omega/ at T/spl les/77 K. The dependence of the heterodyne oscillation linewidth of the R-SQUID on the thermal noise across the shunt resistor is under investigation with a view to the development of an absolute noise thermometer. Signal powers /spl sim/nW have been measured and the device has been shown to be tunable from 5 to 50 MHz. The measured oscillation linewidth (/spl sim/30 kHz at 17 K) is believed to be the narrowest reported for such an HTS device, however non-thermal broadening of the linewidth is also observed, as has been reported for single junctions at GHz frequencies. We describe measurements on such devices over a range of temperatures and bias conditions.