1/f frequency fluctuations in high kinetic inductance CoSi2 microwave cavities

Cobalt disilicide provides a promising nearly epitaxial superconducting material on silicon, which is compatible with high-density integrated circuit technology. We have characterized CoSi2 superconducting microwave cavities around 5.5 GHz for resonance frequency fluctuations at temperatures of 10–200 mK. Comparing with materials used in kinetic inductance detectors, we found relatively weak fluctuations  following the spectral density A/fγ, with A ≃ 6 × 10−16 and γ slightly below 1 at an average number of photons of 30; the noise decreased with measurement power as 1/P1/2. The connection of the frequency fluctuations to two-level states and kinetic inductance fluctuations due to resistance noise is discussed.

Read the whole article by Zeng et al. in APL Quantum.