First Results from ABRACADABRA-10 cm: A Search for Sub-$\mu$eV Axion Dark Matter

The axionis a promising dark mattercandidate, which was originally proposed to solve the strong-CP problemin particle physics. To date, the available parameter space for axionand axion-like particle dark matteris relatively unexplored, particularly at masses $m_a\lesssim1\,\mu$eV. ABRACADABRA is a new experimental program to search for axion dark matterover a broad range of masses, $10^{-12}\lesssim m_a\lesssim10^{-6}$ eV. ABRACADABRA-10 cm is a small-scale prototype for a future detector that could be sensitive to the QCD axion. In this Letter, we present the first results from a 1 month search for axionswith ABRACADABRA-10 cm. We find no evidence for axion-like cosmic dark matterand set 95% C.L. upper limits on the axion-photon coupling between $g_{a\gamma\gamma}<1.4\times10^{-10}$ GeV$^{-1}$ and $g_{a\gamma\gamma}<3.3\times10^{-9}$ GeV$^{-1}$ over the mass range $3.1\times10^{-10}$ eV - $8.3\times10^{-9}$ eV. These results are competitive with the most stringent astrophysical constraints in this mass range.