First Results from ABRACADABRA-10 cm: A Search for Sub-μeV Axion Dark Matter
The axion is a promising dark matter candidate, which was originally proposed to solve the strong-$CP$ problem in particle physics. To date, the available parameter space for axion and axionlike particle dark matter is relatively unexplored, particularly at masses ${m}_{a}\ensuremath{\lesssim}1\text{ }\text{ }\ensuremath{\mu}\mathrm{eV}$. ABRACADABRA is a new experimental program to search for axion dark matter over a broad range of masses, ${10}^{\ensuremath{-}12}\ensuremath{\lesssim}{m}_{a}\ensuremath{\lesssim}{10}^{\ensuremath{-}6}\text{ }\text{ }\mathrm{eV}$. 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 axions with ABRACADABRA-10 cm. We find no evidence for axionlike cosmic dark matter and set 95% C.L. upper limits on the axion-photon coupling between ${g}_{a\ensuremath{\gamma}\ensuremath{\gamma}}<1.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ and ${g}_{a\ensuremath{\gamma}\ensuremath{\gamma}}<3.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$ over the mass range $3.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}--8.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}\text{ }\text{ }\mathrm{eV}$. These results are competitive with the most stringent astrophysical constraints in this mass range.