Metamaterials and Photonic Crystals

cup Negative refraction - may lead to surprising effects! Metamaterials (artificial materials) can exhibit electromagnetic characteristics unlike those of any conventional materials. Negative refraction and artificial magnetism are some examples of properties that can be obtained and controlled in these materials.
In general, metamaterials are supposed to have the characteristic length scale of constituting elements much smaller than the radiation wavelength. They therefore can in good approximation be considered as continuous media with some effective electrodynamic properties.
Photonic crystals are strictly periodic structures with periods similar to the wavelength. This similarity leads to some unusual effects like waveguiding of light, anomalous refraction etc.

Negative Refraction
Negative refraction in Ferromagnet / Superconductor superlattices
According to the basic idea a material with sumultaneously negative dielectric permittivity and magnetic permeabilily would reveal negative refraction, i.e. negative phase velocity. In agreement with this  idea the superlattices ferromagnet/superconductor YBCO/LSMO would reveal negative refraction. In these systems the superconducting YBa2Cu2O7 layers are responsible for the negative dielectric permittivity. The ferromagnetic (La:Sr)MnO3 provide negative magnetic permeability close to the resonance (left panel). With both conditions fulfilled the negative refractive index is realized (right panel, Phys. Rev. Lett. 95, 247009 (2005)).
More rigorous calculations show that weaker conditions for the negative refraction can be realized. In case of metals negative magnetic permeability is a sufficient condition for negative refractive index. In this sence all ferromagnetic metals may reveal negative refraction close to the ferromagnetic resonance. Recently we could prove this condition for Iron and Cobalt.

perfect magnetoelectric
Metamaterials as perfect magnetoelectrics
Perfect magnetoelectrics are materials in which magnetoelectric susceptibility equals the geometric average of electric and magnetic susceptibilities (χme)2 = χeχm. Conventional magnetoelectrics show the values of χme far below the theoretically allowed. Recently we could show that the metamaterials made of split ring resonators can indeed reach the perfect value of the magnetoelectric susceptibility [arXiv:1004.4524].

Selected publications