Wire metamaterial filled metallic resonators

TL;DR

This paper investigates the electromagnetic properties of wire medium filled resonators used in dark matter searches, demonstrating that their quality factors can be higher than previously thought and confirming findings with experiments.

Contribution

The study validates the homogenization model for wire medium resonators and provides experimental confirmation of higher quality factors at room temperature.

Findings

Homogenization model applies without mesoscopic corrections.

Quality factor Q can reach thousands at room temperature.

Experimental results confirm theoretical predictions.

Abstract

In this work we study electromagnetic properties of a resonator recently suggested for the search of axions - a hypothetical candidate to explain dark matter. A wire medium loaded resonator (called a plasma haloscope when used to search for dark matter) consists of a box filled with a dense array of parallel wires electrically connected to top and bottom walls. We show that the homogenization model of wire medium works for this resonator without mesoscopic corrections, and that the resonator quality $Q$ at the frequency of our interest drops versus the growth of the resonator volume $V$ until it is dominated by resistive losses in the wires. We find that even at room temperature metals like copper can give quality factors in the thousands, an order of magnitude higher than originally assumed. Our theoretical results for both loaded and unloaded resonator quality factors were confirmed by building an experimental prototype. We discuss ways to further improve WM loaded resonators.