Candidates for μ<0, ε<0 nanostructures

Recent interest has been generated in composite materials for which both the dielectric constant and the magnetic permeability are negative. These composites behave as if they possess a negative index of refraction, although the broader, less specific adjective "left-handed" has also been applied to them. Such composites possess two sets of structures which axe separately responsible for the negative epsilon and mu. However, materials having a negative mu are common in the microwave frequency range and such a material can replace one set of structures in the composite. An example of a simple composite is a YIG medium (mu <0) penetrated by sets of metallic strips or wires which give rise a negative dielectric constant in the appropriate frequency range. The index of refraction of the composite can be modulated by adjusting the applied magnetic field.