1/f frequency fluctuations due to kinetic inductance in CoSi${}_2$ microwave cavities

Abstract

Cobalt disilicide provides a promising nearly-epitaxial superconducting material on silicon, which is compatible with high-density integrated circuit technology. We have characterized CoSi${}_2$ superconducting microwave cavities around 5.5 GHz for resonance frequency fluctuations at temperatures 10 - 200 mK. We found relatively weak fluctuations $(\delta f/f{)}^2$ following the spectral density $A/f^{\gamma }$, with $A\simeq 6\times 10^{-16}$ and $\gamma$ slightly below 1 at an average number of photons of $10^4$; the noise decreased with measurement power as $1/P^{1/2}$. We identify the noise as arising from kinetic inductance fluctuations and discuss possible origins of such fluctuations.

6 pages, 3 figures