Behavior of the dc Impedance of an rf-Biased Resistive SQUID | NIST

Franco Bordoni, I. Modena, Romani G. L. +1 more

S.S. Tinchev, P. Gutmann

Deborah van Vechten, Robert J. Soulen, Rick Peterson

The authors measured the dc impedance of an rf-biased R-SQUID as a function of applied dc bias current, rf frequency and amplitude, and the critical current of the weak link. They conclude that the inclusion of an rf driving current, as required for parametric upconversion influences, in an as-yet incompletely modeled way, the dc impedance of an R-SQUID.

Deborah van Vechten, Robert J. Soulen, Rick Peterson

Heikki Seppä

The tank circuit noise in an rf-biased R-SQUID noise thermometer is shown to have a small but a detectable influence on the dc impedance of the resistively shunted Josephson junction. The result supplements earlier calculations which have been used to explain some of the experimentally observed characteristics of the dc impedance.

Heikki Seppä

The dc -impedance of an rf-biased R-SQUID is studied analytically for the nonhysteretic regime. A mathematical analysis of the intrinsic behavior of an R-SQUID, including the mutual interaction between the tank circuit and the SQUID loop, is presented. The results obtained give good agreement with some experimentally observed features. Although the main aim of the present paper was to find an analytic solution for the dc -impedance of an R-SQUID, the results given here can also be used to estimate the R-SQUID parameters and to optimize the performance of a R-SQUID noise thermometer. The theory presented here also provides a good basis for modelling the noise properties of a Josephson junction noise thermometer.