Current and temperature controlled variable inductance in superconducting microstrip lines

The inductance of superconducting microstrip lines is measured both as a function of current and temperature. The measurements are performed at 10 MHz for both meander and straight lines by using a multi-frequency LCR meter. The normal state resistance is observed to follow a linear temperature dependence with a slope of 3.59/spl times/10/sup -3//K for the straight line and with a slope of 2.96/spl times/10/sup -3//K for the meander line. The change in inductance is well described by a quadratic dependence on temperature. This result is consistent with an unconventional pairing state. As for the dependence on the bias current, the inductance shows a squared dependence on the bias current. The results for the current- and temperature-controlled inductance are in good agreement with an equation derived using the Ginzburg-Landau theory for the case of thin films.