Axion Search with a Quantum-Limited Ferromagnetic Haloscope

Area of Science:

• Particle Physics
• Cosmology
• Astrophysics
• Quantum Sensing

Background:

• Dark matter constitutes a significant portion of the universe's mass, and axions are leading candidates.
• Detecting axions requires sensitive instruments capable of probing their weak interactions with matter.
• Previous axion searches have explored various detection strategies, each with limitations in sensitivity or mass range.

Purpose of the Study:

• To search for dark matter axions by detecting their interaction with electronic spins using a ferromagnetic axion haloscope.
• To establish new, stringent limits on the axion-electron coupling constant (g_aee).
• To demonstrate a novel method for wide-range axion mass scanning.

Main Methods:

• Employed a photon-magnon hybrid system as an axion-to-electromagnetic field transducer.
• Utilized a quantum-limited Josephson parametric amplifier as a sensitive radio frequency (rf) detector.
• Configured ten yttrium iron garnet spheres within a microwave cavity, coupled by a static magnetic field.

Main Results:

• Achieved the highest sensitivity for an rf spin magnetometer, reaching a minimum detectable field of 5.5×10⁻¹⁹ T.
• Set the best limit on the axion-electron coupling constant to g_aee ≤ 1.7×10⁻¹¹ at 95% confidence level.
• Covered a frequency span of 120 MHz, corresponding to axion masses between 42.4–43.1 μeV.

Conclusions:

• The developed ferromagnetic axion haloscope provides the most sensitive probe to date for axion-electron interactions.
• The experiment significantly improves constraints on dark matter axions within the explored mass range.
• This work demonstrates the first apparatus capable of wide axion-mass scanning solely by adjusting the static magnetic field.