Exploration of Wire Array Metamaterials for the Plasma Axion Haloscope

TL;DR

This paper investigates wire array metamaterials as a promising alternative to traditional microwave cavities for high-frequency axion dark matter searches, demonstrating their tunability and high quality factors.

Contribution

It provides experimental validation of wire array metamaterials' properties and their potential for scalable, tunable resonators in axion detection.

Findings

Excellent agreement with theoretical models for $S_{21}$ measurements.

Projected quality factors of order $10^{4}$ for axion searches.

Practical schemes for tuning the array over 30% frequency range.

Abstract

A plasma haloscope has recently been proposed as a feasible approach to extend the search for dark matter axions above 10 GHz ($\sim$ 40 $\mu$eV), whereby the microwave cavity in a conventional axion haloscope is supplanted by a wire array metamaterial. As the plasma frequency of a metamaterial is determined by its unit cell, and is thus a bulk property, a metamaterial resonator of any frequency can be made arbitrarily large, in contrast to a microwave cavity which incurs a steep penalty in volume with increasing frequency. We have investigated the basic properties of wire array metamaterials through $S_{21}$ measurements in the 10 GHz range. Excellent agreement with theoretical models is found, by which we project achievable quality factors to be of order $10^{4}$ in an actual axion search. Furthermore, schemes for tuning the array over a usable dynamic range ($30\%$ in frequency) appear practical from an engineering perspective.