Axion search with a quantum-limited ferromagnetic haloscope
Abstract
A ferromagnetic axion haloscope searches for Dark Matter in the form of axions by exploiting their interaction with electronic spins. It is composed of an axion-to-electromagnetic field transducer coupled to a sensitive rf detector. The former is a photon-magnon hybrid system, and the latter is based on a quantum-limited Josephson parametric amplifier. The hybrid system consists of ten 2.1 mm diameter YIG spheres coupled to a single microwave cavity mode by means of a static magnetic field. Our setup is the most sensitive rf spin-magnetometer ever realized. The minimum detectable field is 5.5×10-19\,T with 9 h integration time, corresponding to a limit on the axion-electron coupling constant gaee1.7×10-11 at 95% CL. The scientific run of our haloscope resulted in the best limit on DM-axions to electron coupling constant in a frequency span of about 120 MHz, corresponding to the axion mass range 42.4-43.1\,μeV. This is also the first apparatus to perform an axion mass scanning by changing the static magnetic field.