We have observed an unusual hysteresis loop in rf power dependence of high-temperature superconductor (HTS) coplanar transmission lines. At 77 K and 1 GHz, the signal transmission was linear (insertion loss <0.1 dB) until the input power (Pin) reached a critical value of Pc=0.4 W. An abrupt drop by ∼37 dB in the transmitted power (Pout) was observed at Pin=Pc followed by a slow increase (P out∝Pin0.62) for Pin> P c. As Pm was then decreased, it retraced the previous curve only until Pin=Pc. However, as Pin was reduced further Pout did not rise until Pin=158 mW, at which Pout started to increase rapidly and returned to the linear regime for Pin<71 mW. Such a sharp transition and a strong hysteresis effect were unique to the HTS line whereas a gold line with an identical structure did not exhibit these characteristics. This behavior may be utilized for potential applications of new HTS microwave power (current) limiters and switches. Several possible origins for the hysteresis effect are proposed and discussed.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)