Anomalous microwave response of high-temperature superconducting thin-film microstrip resonator in weak dc magnetic fields

TL;DR

This study investigates the unusual microwave response of YBCO superconducting microstrip resonators under weak dc magnetic fields, revealing non-monotonic behavior of surface resistance and reactance with implications for superconducting device performance.

Contribution

It provides new insights into the magnetic field dependence of microwave properties in high-temperature superconducting thin films, highlighting a crossover field and impedance behavior.

Findings

Surface resistance and reactance show non-monotonic dependence on H_{dc}.

The crossover field H_{c} is independent of input microwave amplitude and frequency.

Impedance ratio r_{H} changes from 0.6 to 0.1 across H_{c}.

Abstract

We have studied an anomalous microwave (mw) response of superconducting YBa_{2}Cu_{3}O_{7-delta} (YBCO) microstrip resonators in the presence of a weak dc magnetic field, H_{dc}. The surface resistance (R_{s}) and reactance (X_{s}) show a correlated non-monotonic behaviour as a function of H_{dc}. R_{s} and X_{s} were found to initially decrease with elevated H_{dc} and then increase after H_{dc} reaches a crossover field, H_{c}, which is independent of the amplitude and frequency of the input mw signal within the measurements. The frequency dependence of R_{s} is almost linear at fixed H_{dc} with different magnitudes (<H_{c}, =H_{c} and >H_{c}). The impedance plane analysis demonstrates that r_{H}, which is defined as the ratio of the change in R_{s}(H_{dc}) and that in X_{s}(H_{dc}), is about 0.6 at H_{dc}<H_{c} and 0.1 at H_{dc}>H_{c}. The H_{dc} dependence of the surface impedance is qualitatively independent of the orientation of H_{dc}.