Search for axion-like dark matter with spin-based amplifiers

TL;DR

This paper introduces a quantum sensor using hyperpolarized nuclear spins to search for axion-like dark matter, achieving unprecedented sensitivity and setting new constraints on ALP-nucleon interactions over a specific mass range.

Contribution

The authors develop a spin-based amplifier that enhances detection sensitivity for ALPs, surpassing previous laboratory limits by at least five orders of magnitude.

Findings

Set new laboratory limits on ALP-nucleon coupling at 67.5 feV.

Achieved magnetic sensitivity of 18 fT/Hz$^{1/2}$, better than previous magnetometers.

Constrained ALP and dark photon interactions beyond astrophysical bounds.

Abstract

Ultralight axion-like particles (ALPs) are well-motivated dark matter candidates introduced by theories beyond the standard model. However, the constraints on the existence of ALPs through existing laboratory experiments are hindered by their current sensitivities, which are usually weaker than astrophysical limits. Here, we demonstrate a new quantum sensor to search for ALPs in the mass range that spans about two decades from 8.3 feV to 744 feV. Our sensor makes use of hyperpolarized long-lived nuclear spins as a pre-amplifier that effectively enhances coherently oscillating axion-like dark-matter field by a factor of >100. Using spin-based amplifiers, we achieve an ultrahigh magnetic sensitivity of 18 fT/Hz$^{1/2}$, which is significantly better than state-of-the-art nuclear-spin magnetometers. Our experiment constrains the parameter space describing the coupling of ALPs to nucleons over our mass range, at 67.5 feV reaching $2.9\times 10^{-9}~\textrm{GeV}^{-1}$ ($95\%$ confidence level), improving over previous laboratory limits by at least five orders of magnitude. Our measurements also constrain the ALP-nucleon quadratic interaction and dark photon-nucleon interaction with new limits beyond the astrophysical ones