Search for axion-like dark matter with ferromagnets

• Published in: Nature physics Vol. 17; no. 1; pp. 79 - 84
• Main Authors: Gramolin, Alexander V., Aybas, Deniz, Johnson, Dorian, Adam, Janos, Sushkov, Alexander O.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.01.2021; Nature Publishing Group
• Subjects: 639/766/119; 639/766/34/4119; 639/766/419; Atomic; Broadband; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Confidence intervals; Dark matter; Electromagnetic coupling; Electromagnetic interactions; Ferromagnetism; Ferrous alloys; Magnetic fields; Magnets; Mathematical and Computational Physics; Molecular; Nickel; Optical and Plasma Physics; Physics; Physics and Astronomy; Superconducting quantum interference devices; Theoretical
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/s41567-020-1006-6

Ultralight axion-like particles are well-motivated dark matter candidates, naturally emerging from theories of physics at ultrahigh energies. Here we report the results of a direct search for electromagnetic interactions of axion-like dark matter in the mass range that spans three decades from 12 peV to 12 neV. The detection scheme is based on a modification of Maxwell’s equations in the presence of axion-like dark matter that mixes with a static magnetic field to produce an oscillating magnetic field. The experiment makes use of toroidal magnets with ferromagnetic powder cores made of an iron–nickel alloy, which enhance the static magnetic field by a factor of 24. Using superconducting quantum interference devices, we achieve magnetic sensitivity of 150  aT Hz − 1 / 2 , which is at the level of the most sensitive magnetic field measurements demonstrated with any broadband sensor. We recorded 41 h of data and improved the best limits on the magnitude of electromagnetic coupling constant for axion-like dark matter over a part of our mass range, at 20 peV reaching 4.0 × 10 −11  GeV −1 (95% confidence level). Our measurements begin to explore the coupling strengths and masses of axion-like particles, where their mixing with photons could explain the anomalous transparency of the Universe to TeV γ-rays. The presence of axion-like dark matter candidates is expected to induce an oscillating magnetic field, enhanced by a ferromagnet. Limits on the electromagnetic coupling strength of axion-like particles are reported over a mass range spanning three decades.