Anomalous current-dependence of kinetic inductance in ultrathin NbN meander lines

Measurements were conducted on the radio frequency impedance of 10-nm thick superconducting granular NbN meander lines with widths between 5 micrometers and 20 micrometers. A vector network analyzer was employed to determine the complex reflection coefficient. Results reveal that the film's kinetic inductance dominates the impedance. Results also show that the rise of direct current significantly reduces the measured inductance.