Broadband and Resonant Approaches to Axion Dark Matter Detection

TL;DR

This paper proposes a novel experimental method using a toroidal magnet and SQUID magnetometer to detect ultralight axion dark matter, exploring both resonant and broadband readout techniques for improved sensitivity.

Contribution

It introduces a new detection scheme for axion dark matter utilizing a toroidal magnet and compares resonant and broadband readout approaches for the first time.

Findings

Broadband approach offers advantages at small axion masses.

Potential sensitivity to axion-like dark matter in the 10^{-14}-10^{-6} eV range.

Can probe QCD axions with GUT-scale decay constants.

Abstract

When ultralight axion dark matter encounters a static magnetic field, it sources an effective electric current that follows the magnetic field lines and oscillates at the axion Compton frequency. We propose a new experiment to detect this axion effective current. In the presence of axion dark matter, a large toroidal magnet will act like an oscillating current ring, whose induced magnetic flux can be measured by an external pickup loop inductively coupled to a SQUID magnetometer. We consider both resonant and broadband readout circuits and show that a broadband approach has advantages at small axion masses. We estimate the reach of this design, taking into account the irreducible sources of noise, and demonstrate potential sensitivity to axion-like dark matter with masses in the range of 10^{-14}-10^{-6} eV. In particular, both the broadband and resonant strategies can probe the QCD axion with a GUT-scale decay constant.