Wavelike Dark Matter Searches with SRF Cavities*

Dark matter makes up 85% of the matter in the universe and 27% of its energy density, but we don't know what comprises dark matter. Wavelike dark matter, including the QCD axion and dark photons, are well-motivated dark matter candidates that have been receiving more attention in recent years. SRF cavities are a promising way to search for wavelike dark matter candidates with increased sensitivity and scan rate compared to traditional cavities using microwave cavities. This presentation will report on the Superconducting Quantum Materials and Systems (SQMS) Center's various efforts to search for dark matter with SRF cavities. First, we will describe proof-of-principle measurement with a 1.3 GHz Niobium cavity with an ultra-high quality factor (Q~10¹⁰) that has achieved the best sensitivity and deepest exclusion to wavelike dark photon dark matter by almost an order of magnitude. We then describe SQMS efforts to search for wavelike dark matter candidates with tunable SRF cavities that are tolerant to multi-Tesla magnetic fields and quantum sensors that subvert the Standard Quantum Limit.