Tuning the response of YBCO microwave resonators by heavy-ion patterned micro-channels

Channels with micron-size width have been carved in YBa2Cu3O7-x (YBCO) coplanar microwave resonators by micro-collimated swift heavy-ion irradiation at high fluences. The response of the resonators as a function of temperature, magnetic field and input power as well as magneto-optical imaging was used to characterize the properties of such micro-channels. The microwave method proposed to characterize the channels—with dimensions from 1/3200 to 1/178 of the wavelength—is based on the comparison between the fundamental and the first harmonic resonant modes. As expected due to the high irradiation fluence, higher penetration depth, higher microwave resistivity and lower nonlinearity thresholds have been found. In this configuration, it is shown that the micro-channels can be driven into a highly dissipative, nonlinear regime while the rest of the resonator still persists in a linear response. The higher responsivity of the micro-channels with respect to the as-grown YBCO was tested by applying an external magnetic field, showing that a locally applied external control signal can tune the response of the resonators, when properly biased. The possible impact of these results in the field of high temperature superconductor based sensors is discussed.