Tunable Wire Metamaterials for an Axion Haloscope

TL;DR

This paper demonstrates a tunable wire metamaterial system that can adjust its plasma frequency by varying the relative position of two interpenetrating wire lattices, aiding dark matter axion detection.

Contribution

It introduces a practical method to tune the plasma frequency of wire metamaterials via lattice displacement, validated by experiments, theory, and simulations.

Findings

Plasma frequency can be tuned over 16% range.

Experimental results agree with theory and simulations.

The system enables adjustable resonant conditions for axion searches.

Abstract

Metamaterials based on regular two-dimensional arrays of thin wires have attracted renewed attention in light of a recently proposed strategy to search for dark matter axions. When placed in the external magnetic field, such metamaterials facilitate resonant conversion of axions into plasmons near their plasma frequency. Since the axion mass is not known a priori, a practical way to tune the plasma frequency of metamaterial is required. In this work, we have studied a system of two interpenetrating rectangular wire lattices where their relative position is varied. The plasma frequency as a function of their relative position in two dimensions has been mapped out experimentally, and compared with both a semi-analytic theory of wire-array metamaterials and numerical simulations. Theory and simulation yield essentially identical results, which in turn are in excellent agreement with experimental data. Over the range of translations studied, the plasma frequency can be tuned over a range of 16%.