The QUAX proposal: a search of galactic axion with magnetic materials

TL;DR

The paper proposes a novel experimental method to detect galactic axions by measuring their interaction with electron spins in magnetized materials using a SQUID amplifier, aiming to identify axion properties.

Contribution

It introduces the QUAX experimental setup that uses magnetized samples and resonant detection to search for axions, combining magnetic resonance and quantum amplification techniques.

Findings

Design of the QUAX detector concept

Theoretical sensitivity estimates for axion detection

Potential to explore new axion parameter space

Abstract

Aim of the QUAX (QUaerere AXion) proposal is to exploit the interaction of cosmological axions with the spin of electrons in a magnetized sample. Their effect is equivalent to the application of an oscillating rf field with frequency and amplitude which are fixed by axion mass and coupling constant, respectively. The rf receiver module of the QUAX detector consists of magnetized samples with the Larmor resonance frequency tuned to the axion mass by a polarizing static magnetic field. The interaction of electrons with the axion-equivalent rf field produces oscillations in the total magnetization of the samples. To amplify such a tiny field, a pump field at the same frequency is applied in a direction orthogonal to the polarizing field. The induced oscillatory magnetization along the polarizing field is measured by a SQUID amplifier operated at its quantum noise level.