Axion dark matter detection by superconducting resonant frequency conversion

A bstract We propose an approach to search for axion dark matter with a specially designed superconducting radio frequency cavity, targeting axions with masses m a ≲ 10 − 6 eV. Our approach exploits axion-induced transitions between nearly degenerate resonant modes of frequency ∼ GHz. A scan over axion mass is achieved by varying the frequency splitting between the two modes. Compared to traditional approaches, this allows for parametrically enhanced signal power for axions lighter than a GHz. The projected sensitivity covers unexplored parameter space for QCD axion dark matter for 10 − 8 eV ≲ m a ≲ 10 − 6 eV and axion-like particle dark matter as light as m a ∼ 10 − 14 eV.