  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%.
