Ultralight Dark Matter Detection with a Ferromagnet Lattice

TL;DR

This paper proposes a ferromagnet lattice magnetometer to detect ultralight dark matter by coherently combining multiple levitated ferromagnets, significantly improving sensitivity and surpassing existing constraints across a broad mass range.

Contribution

Introducing a ferromagnet lattice system that enhances ULDM detection sensitivity by suppressing interactions and leveraging collective readout, outperforming single-ferromagnet setups.

Findings

Enhanced sensitivity to ULDM signals over existing methods.

Effective suppression of magnetic dipole interactions via high-frequency fields.

Favorable scaling of noise properties with the number of ferromagnets.

Abstract

A levitated ferromagnet provides an exceptionally sensitive probe of ultralight dark matter (ULDM) through measuring weak magnetic-like field signals. We propose a ferromagnet lattice magnetometer that coherently combines multiple levitated ferromagnets to enhance effective sensitivity. By replacing a single ferromagnet with a lattice, we increase the total polarized spin while preserving the intrinsic dynamical response of each constituent ferromagnet. We show that magnetic dipole-dipole interactions within the lattice can be dynamically suppressed through a high-frequency magnetic field, rendering the system effectively noninteracting, at the cost of only a moderate reduction in signal amplitude due to the distinct renormalization of linear and quadratic spin responses. We analyze the noise properties of the lattice and demonstrate that collective readout leads to favorable scaling with the number of ferromagnets. Interpreted in terms of axion-electron, dark photon, and axion-photon couplings, our results yield projected sensitivities that significantly exceed existing single-ferromagnet implementations. In particular, for axion-photon interactions, we find a nontrivial lattice-induced enhancement of the signal itself, leading to sensitivities that surpass existing constraints over a broad mass range.