Sensitivity of Proposed Search for Axion-induced Magnetic Field using Optically Pumped Magnetometers

TL;DR

This paper explores a room-temperature method using optically pumped magnetometers to detect axion-induced magnetic fields, potentially improving current limits on axion-photon coupling in a specific mass range.

Contribution

It proposes modifying existing MRI setups with optically pumped magnetometers to search for axions, achieving sensitivity beyond current experimental limits.

Findings

Existing MRI-based setup sensitive to $10^{-7}$ GeV$^{-1}$ coupling at $3\times10^{-10}$ eV.

Realistic modifications could improve sensitivity by up to three orders of magnitude.

The method avoids cryogenic systems, enabling room-temperature axion searches.

Abstract

We investigate a search for the oscillating current induced by axion dark matter in an external magnetic field using optically pumped magnetometers (OPMs). This experiment is based upon the LC circuit axion detection concept of Sikivie, Sullivan, and Tanner. The modification of Maxwell's equations caused by the axion-photon coupling results in a minute oscillating magnetic field at the frequency equal to the axion mass in the presence of magnetic field. This induced magnetic field could be searched for using an LC circuit amplifier with an OPM, the most sensitive cryogen-free magnetic-field sensor, in a room temperature experiment, avoiding the need for a complicated and expensive cryogenic system. We discuss how an existing magnetic resonance imaging (MRI) experiment can be modified to search for axions in a previously unexplored part of the parameter space. Our existing detection setup, optimized for MRI, is already sensitive to an axion-photon coupling of $10^{-7}$ GeV$^{-1}$ for an axion mass near $3\times10^{-10}$ eV. While this is ruled out by limits from astrophysics and solar axion searches, we show that realistic modifications, and optimization of the experiment for axion detection, can set a new limit on the axion-photon coupling up to three orders of magnitude beyond the current best limit, for axion masses between $10^{-11}$ eV and $10^{-7}$ eV.ion masses between $10^{-11}$ eV and $10^{-7}$ eV.